Investigating Applicability of Evaporative Cooling Systems for Thermal Comfort of Poultry Birds in Pakistan

applied sciences

Article Investigating Applicability of Evaporative Cooling Systems for Thermal Comfort of Poultry Birds in Pakistan

Haﬁz M. U. Raza 1, Hadeed Ashraf 1, Khawar Shahzad 1, Muhammad Sultan 1,* , Takahiko Miyazaki 2,3, Muhammad Usman 4,* , Redmond R. Shamshiri 5 , Yuguang Zhou 6 and Riaz Ahmad 6 1 Department of Agricultural Engineering, Bahauddin Zakariya University, Bosan Road, Multan 60800, Pakistan; [email protected] (H.M.U.R.); [email protected] (H.A.); [email protected] (K.S.) 2 Faculty of Engineering Sciences, Kyushu University, Kasuga-koen 6-1, Kasuga-shi, Fukuoka 816-8580, Japan; [email protected] 3 International Institute for Carbon-Neutral Energy Research (WPI-I2CNER), Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan 4 Institute for Water Resources and Water Supply, Hamburg University of Technology, Am Schwarzenberg-Campus 3, 20173 Hamburg, Germany 5 Leibniz Institute for Agricultural Engineering and Bioeconomy, Max-Eyth-Allee 100, 14469 Potsdam-Bornim, Germany; [email protected] 6 Bioenergy and Environment Science & Technology Laboratory, College of Engineering, China Agricultural University, Beijing 100083, China; [email protected] (Y.Z.); [email protected] (R.A.) * Correspondence: [email protected] (M.S.); [email protected] (M.U.); Tel.: +92-333-610-8888 (M.S.); Fax: +92-61-9210298 (M.S.) Received: 4 June 2020; Accepted: 24 June 2020; Published: 28 June 2020

Abstract: In the 21st century, the poultry sector is a vital concern for the developing economies including Pakistan. The summer conditions of the city of Multan (Pakistan) are not comfortable for poultry birds. Conventionally, swamp coolers are used in the poultry sheds/houses of the city, which are not efficient enough, whereas compressor-based systems are not economical. Therefore, this study is aimed to explore a low-cost air-conditioning (AC) option from the viewpoint of heat stress in poultry birds. In this regard, the study investigates the applicability of three evaporative cooling (EC) options, i.e., direct EC (DEC), indirect EC (IEC), and Maisotsenko-cycle EC (MEC). Performance of the EC systems is investigated using wet-bulb effectiveness (WBE) for the climatic conditions of Multan. Heat stress is investigated as a function of poultry weight. Thermal comfort of the poultry birds is calculated in terms of temperature-humidity index (THI) corresponding to the ambient and output conditions. The heat production from the poultry birds is calculated using the Pederson model (available in the literature) at various temperatures. The results indicate a maximum temperature gradient of 10.2 ◦C (MEC system), 9 ◦C (DEC system), and 6.5 ◦C (IEC systems) is achieved. However, in the monsoon/rainfall season, the performance of the EC systems is significantly reduced due to higher relative humidity in ambient air.

Keywords: evaporative cooling; poultry birds; heat production; temperature-humidity-index; Pakistan

1. Introduction Air-conditioning (AC) is the process of controlling temperature and humidity of ambient air to achieve thermal comfort for a range of occupants [1,2]. It involves various processes to condition the

Appl. Sci. 2020, 10, 4445; doi:10.3390/app10134445 www.mdpi.com/journal/applsci Appl. Sci. 2020, 10, 4445 2 of 18 ambient air, which includes cooling, heating, humidification, dehumidification, and ventilation [3]. Applications of the AC are not only limited to humans’ thermal comfort but also to agricultural products’ storage and livestock applications [4]. Livestock sector as a part of agriculture sector is of prime importance for any growing economy [5]. It includes animal farming for meat and milk production as well as poultry farming for meat and egg production [6]. According to Pakistan Statistical Yearbook [7], the poultry sector under the agriculture sector contributed 1.4% in overall gross domestic product (GDP) of the country during economical year 2017–2018 [7]. Out of total meat production (i.e., 4.3 million tons), 1.47 million tons poultry meat is produced in the country, which highlighted the significance of the poultry sector in the economy [7]. In a poultry farm, cooling and ventilation of surrounding air are necessary for optimum growth of poultry birds [8]. These birds are highly susceptible to slight fluctuation in temperature and humidity of the surrounding air [8]. The poultry birds require an optimum temperature-humidity index (THI) throughout their growth up to the meat harvest stage. To achieve the required THI for the poultry birds, ambient air is conditioned. Several types of cooling systems are being used to attain thermal comfort of the poultry birds [3]. In Pakistan, pad type direct evaporative cooling (DEC) system is commonly preferred for cooling of air in poultry farms [9]. Typical hot and dry conditions of the country move to hot and humid conditions in the monsoon (i.e., heavy rainfall) season, which result in higher relative humidity in ambient air. This, therefore, limits the performance of a standalone DEC system [10]. Consequently, advanced evaporative cooling (EC) systems, namely the indirect evaporative cooling (IEC) system and the Maisotsenko-cycle based cooling (MEC) system, can be a better option for poultry farming in Pakistan [11]. EC systems are power-efficient when compared to conventional vapor compression air-conditioning systems in hot and dry climatic conditions [1,12]. The EC systems are simple in design (structure), energy efficient, and environmentally-friendly as compared to traditional vapor compression air-conditioning (VCAC) systems. The AC systems being traditionally used across the world consume a major share of primary energy and exhaust hydrochlorofluorocarbon-carbons (HCFCs)/hydro-fluorocarbons (HFCs)/chlorofluorocarbons (CFCs) [13–16]. Alternatively, HCFC, HFC, and CFC free refrigerants and desiccant unit based AC systems are also being studied [17,18]. Whereas, the EC systems have a very low carbon footprint when compared to the VCAC systems [19,20]. Objectives of this study include performance evaluation of three types of EC systems for the climatic conditions of Multan (Pakistan) and feasibility analysis of these EC systems for thermal comfort based on THI of poultry birds in poultry houses across Multan.

2. Thermal Comfort for Poultry Birds Temperature and humidity control are necessary for every human and non-human’s thermal comfort [4]. Additionally, the poultry birds also require an optimum temperature and relative humidity conditions for healthy growth [21]. Hence, seasonal variation in weather demands the need for AC. Figure1 shows thermoneutral zones for poultry birds and represents the physical e ffect of heat stress on the poultry (broiler) birds [22]. Three different temperature zones are mentioned as thermoneutral, upper, and lower critical temperature zones. Optimum physiological growth in the birds increases with the optimum range of temperature and humidity inside the poultry house. Compared to the human body, the poultry birds lack sweat glands to dissipate body heat in a heat-stressed environment [21]. The birds transfer excess heat from their body into the environment by panting (i.e., heavy breathing) once the thermoneutral zone is crossed [21]. During the panting process, the birds transfer additional moisture into the environment, which leads to their suffocating conditions. Once the environment reaches a maximum heat point (i.e., dry-bulb temperature 47 C[23]), the birds expire due to extreme ≥ ◦ stress heat. Figure2 shows psychrometric representation of the required optimum temperature and relative humidity conditions for the birds (i.e., broilers) of varying age, and hourly climatic distribution of Multan. One-day-old chicks need relatively more temperature as compared to the elder chickens, as dictated by local practice of using heaters for one week. The optimum temperature slides down Appl. Sci. 2020, 10, 4445 3 of 18

from 34 to 32 ◦C, 32 to 28 ◦C, 28 to 26 ◦C, 26 to 24 ◦C, and 24 to 20 ◦C for one, two, three, four, and five week-old chickens, respectively [24,25]. At the same time, the relative humidity (RH) is maintained Appl. Sci. 2020, 10, x FOR PEER REVIEW 3 of 18 atAppl. 50–70% Sci. 2020 throughout, 10, x FOR PEER the REVIEW growth period [24,25]. In the poultry house, heat load is contributed3 of by 18 metabolism and respiration of the broiler, structure of the building (through convection), air change the building (through convection), air change through doors, and sunlight through windows [26]. To throughthe building doors, (through and sunlight convection) through, air windows change through [26]. To doors satisfy, and the sun thermallight through comfort needswindows for poultry[26]. To satisfy the thermal comfort needs for poultry birds, a comprehensive AC system is needed to be birds,satisfy athe comprehensive thermal comfort AC needs system for is neededpoultry tobirds, be installeda comprehensive in the poultry AC system house, is which needed has to thebe installed in the poultry house, which has the potential to achieve the required heat loads. In this potentialinstalled toin achievethe poultry the required house, heatwhich loads. has Inthe this potential study, the to workingachieve the principle required of di heatfferent loads EC. systems In this study,study, the the w workingorking principle principle of of different different EC EC systems systems is is explained explained and and their their respective respective performance performance foris explainedpoultry air and-conditioning their respective is investigated performance including for poultry the effect air-conditioning of temperature, is investigated relative humidity including, thefor epoultryffect of temperature,air-conditioning relative is investigated humidity, and including velocity the on effect the growth of temperature, of poultry birds.relative humidity, andand velocity velocity on on the the growth growth of of poultry poultry birds birds. .

Lower Upper MaximumMaximum Lower Upper Death from critical heat Death from criticalcritical critical heat Fast panting SlowSlow Fast panting physical pantingpanting physical Thermoneutrol zone - -BirdsBirds can't can'tcontrollcontroll Thermoneutrol zone body temprature - normal behaviour HeatHeat related related body temprature - normal behaviour welfare problem - welfare problem - -regulateregulate heat heat loss loss welfare problem - welfare problem Increasing ambient temperature Increasing ambient temperature FigureFigure 1. 1. A A simplified simplified simpliﬁed scheme scheme showing showing thermoneutral thermoneutral zone zone of of poultry poultry birds. birds.

Figure 2. Psychrometric distribution of climatic conditions (hourly basis) of Multan associated with Figure 2.2. PsychrometricPsychrometric distribution of climatic conditions (hourly basis) of MultanMultan associatedassociated withwith thermal comfort zones of poultry birds. thermalthermal comfortcomfort zoneszones ofof poultrypoultry birds.birds.

InInIn orderorder to toto achieve achieveachieve required required required temperature temperaturetemperature and humidity and and humidity humidity level inside levellevel poultry inside inside houses, poultry poultry the houses houses ventilation, , thethe vrateventilationentilation and air rate rate velocity and and air air are velocity velocity of paramount are are of of paramount paramount importance importan importan [27]. Ventilationcece [27] [27]. Ventilation. Ventilation generally mitigatesgenerally generally themitigates mitigates respiratory the the respiratoryandrespiratory humidity-related and and humidity humidity issues-related-related and replaces issues issues fouland and gases replaces replaces to increase foul foul gases gases the productivityto to increase increase of the the broilers. productivity productivity Factors ofto of broilers.markbroilers. the F Factors productivityactors to to mark mark are the the feed productivity productivity intake, feed are are conversion feed feed intake, intake, ratio, feed feed and conversion conversion body weight ratio, ratio, gain and and [28 body ].body Any weight weight slight gainvariationgain [28] [28]. .Any inAny temperature, slight slight variation variation humidity, in in te temperaturemperature and air velocity, ,humidity humidity results, ,and and in air poultry air velocity velocity (health) results results welfare in in poultry poultry issues (health) [(health)29]. welfarewelfare issues issues [29] [29]. .

Appl. Sci. 2020, 10, 4445 4 of 18 Appl. Sci. 2020, 10, x FOR PEER REVIEW 4 of 18

3. Material Materialss and and Methods Methods

33.1..1. Evaporative Evaporative Cooling Cooling (EC) (EC) Systems Systems TThreehree kindskinds ofof lab-scalelab-scale experimental experimental EC EC systems systems were were developed developed as shownas shown in Figure in Figure3. There 3. There was wasa similar a similar housing housing assembly assembly used used for diforff erentdifferent heat heat mass mass exchangers exchangers (i.e., (i.e. IEC, IEC and and MEC MEC channels) channels) for forexperimentation. experimentation The. directThe direct (DEC), (DEC), indirect indirect (IEC), and (IEC), M-cycle and (MEC) M-cycle evaporative (MEC) coolingevaporative systems cooling were systemsoperated were for di operatedfferent conditions for different and conditions the experimental and the experimental data of temperature data of andtemperature relative humidity and relative for humiditythe climatic for conditions the climatic of Multanconditions (Pakistan) of Multan was (Pakistan) collected. was Performance collected. of Performance the systems of was the evaluated systems wasin terms evaluated of the in temperature terms of the gradient temperature (i.e., digradientfference (i.e. between, difference ambient between and supplyambient air and temperature) supply air temperatureand relative) humidity and relative (RH) humidity level (of the (RH) ambient level and (of the supply ambient air) to and investigate supply air)the thermalto investigate comfort the of thermalpoultry birds.comfort In of Figure poultry3, pictorial birds. In representations Figure 3, pictorial of the representation developed experimentals of the developed systems experimental along with systemsMEC and along IEC channels with MEC are presented. and IEC channels It consists are of apresented. fan, moisture It consists sensor, temperature of a fan, moisture sensor, velocitysensor, temperaturesensor, and water sensor storage, velocity tank. sensor, Additionally, and water experiments storage tank. of theAdditionally, DEC system experiment with celluloses of the cooling DEC systempads (or with more cellulose commonly cooling known pads as (or honeycomb more commonly pads) wasknown used as for honeycomb this experiment pads) was instead used of for aspen this experimentwood fiber containedinstead of inaspen a net wood (local fiber name contained “khas”). in The a net detailed (local scientific name “khas”) concept. The and detail thermodynamiced scientific conceptfundamentals and thermodynamic of these developed fundamentals EC systems of are these described developed in the coming EC systems subheadings. are described in the coming subheadings. MEC IEC

Supply pipe Water tank

Product air a

Process air

x Heat and mass exchanger Temperature and Temperature and

A moisture sensor Pump moisture sensor

Water sump

Figure 3. AA p pictorialictorial representation representation of the e experimentalxperimental apparatus for MEC and IEC EC systems systems..

3.1.1. Direct Direct EC EC (DEC) (DEC) S Systemystem Direct evaporative evaporative cooling cooling (DEC) (DEC) system system is is the the simplest simplest and and old old type type of ofEC EC system system in which in which air comesair comes directly directly in incontact contact with with the the water water surface surface to to reduce reduce its its temperature [[30,31]30,31].. Continuous evaporation of of water water (adiabatic (adiabatic process) process) vapors vapors causes causes a cooling a cooling effect eﬀect up up to toa saturation a saturation point point of air of [1,3,32]air [1,3., 32Enthalpy]. Enthalpy (kJ/kg (kJ) of/kg) air ofat inlet air at and inlet outlet and conditions outlet conditions remains remainsthe same the, whereas same, the whereas humidity the ratiohumidity (gram ratio of water (gram per of water kg of perdry kgair of i.e. dry g/kgDA air i.e.,) gincreases/kgDA) increases.. The DEC The system DEC can system potentially can potentially reduce thereduce temperature the temperature of the inlet of theair inletup toair its upwet to-bulb its wet-bulbtemperature temperature with wet- withbulb wet-bulbeffectiveness eﬀectiveness (WBE) of 75(WBE)%-95% of 75–95%[3,33]. Schematic [3,33]. Schematic and psychrometric and psychrometric representation representation of the DEC of the system DEC systemis shown is in shown Figure in 4Figure(a). 4a. Cooling effect in the DEC system is produced by utilizing latent heat of evaporation governed by Equation (1) given in the literature [3]. Appl. Sci. 2020, 10, x FOR PEER REVIEW 5 of 18

ℎ표푢푡푙푒푡 = 1.006 푇푑푏 + 푤(2501 + 1.86푇푑푏) (1) where houtlet represents enthalpy of the outlet air (kJ/kg), Tdb denotes dry-bulb temperature of the air (°C), and w represents the humidity ratio of the outlet air (kg/kg). For further study on DEC, Equations (2)-(3) provide more insight [3].

(퐷퐵푇)표푢푡푙푒푡 ≥ (푊퐵푇)푖푛푙푒푡 (2)

(푅퐻)표푢푡푙푒푡 > (푅퐻)푖푛푙푒푡 (3) where DBT denotes dry-bulb temperature air (°C), RH denotes relative humidity of air (%), and subscripts outlet and inlet represent outlet and inlet air conditions, respectively.

3.1.2. Indirect EC (IEC) System Indirect evaporative cooling (IEC) system is a system in which heat and mass transfer take place to reduce the temperature of primary/ambient air without the addition of moisture. It works on the basis of sensible cooling [1]. It consists of two channels named wet and dry channels [34]. Primary air passes through a dry channel and secondary/process air passes through a wet channel. In the IEC system, a cooling effect is produced by a two-way thermodynamic process: (1) isenthalpic cooling in the wet channel by water evaporation, and (2) sensible heat transfer in the dry channel [1,35]. It can reduce the temperature up to the wet-bulb temperature. Therefore, its WBE range is 50-65% [36,37]. In the IEC system, humidity (g/kg of dry air DA) of inlet air and outlet air remains the same. However, enthalpy (kJ/kg of dry air DA) of outlet air is decreased [1]. Schematic and psychrometric representationAppl. Sci. 2020, 10, 4445of the IEC system is shown in Figure 4(b). Further insights into the IEC system5 ofare 18 governed by Equations (4)-(7) given in the literature [3].

DEC IEC

dry channel (2 (2) (1) (1) wet channel (3 wet channel (1)

T W2 W 1. inlet air wb(2) Tout (3) Texhaus 2 T 2. outlet air 1. inlet air wb

Tdp Tin 2. outlet air Tdp T Tout in 3. exhaust air

(1) W1 (2) (1) W1

Humidity Humidity ratio [g/kg ofDA] Humidity Humidity ratio [g/kg ofDA]

Dry bulb temprature Dry bulb temprature (a) (b)

MEC

(1) dry channel (2)

(2) (1) wet channel (3) Texhaus (3 (1) W2 dry channel Twb

1. inlet air Tin Tdp Tout 2. outlet air (2) (1) W1

3. exhaust air Humidity ratio [g/kg ofDA]

Dry bulb temprature (c)

Figure 4. TheThe s schematicchematic and and psychrometric psychrometric representation representationss of of the the EC EC systems systems for for ( (aa)) DEC, DEC, ( (bb)) IEC, IEC, and ( c) MEC configurations conﬁgurations..

Cooling eﬀect in the DEC system is(퐷퐵푇 produced)표푢푡푙푒푡 by≥ utilizing(푊퐵푇)푖푛푙푒푡 latent heat of evaporation governed(4) by Equation (1) given in the literature [3].

houtlet = 1.006 Tdb + w(2501 + 1.86Tdb) (1) where houtlet represents enthalpy of the outlet air (kJ/kg), Tdb denotes dry-bulb temperature of the air (◦C), and w represents the humidity ratio of the outlet air (kg/kg). For further study on DEC, Equations (2) and (3) provide more insight [3].

(DBT) (WBT) (2) outlet ≥ inlet

(RH)outlet > (RH)inlet (3) where DBT denotes dry-bulb temperature air (◦C), RH denotes relative humidity of air (%), and subscripts outlet and inlet represent outlet and inlet air conditions, respectively.

3.1.2. Indirect EC (IEC) System Indirect evaporative cooling (IEC) system is a system in which heat and mass transfer take place to reduce the temperature of primary/ambient air without the addition of moisture. It works on the basis of sensible cooling [1]. It consists of two channels named wet and dry channels [34]. Primary air passes through a dry channel and secondary/process air passes through a wet channel. In the IEC system, a cooling eﬀect is produced by a two-way thermodynamic process: (1) isenthalpic cooling in the wet channel by water evaporation, and (2) sensible heat transfer in the dry channel [1,35]. It can reduce the temperature up to the wet-bulb temperature. Therefore, its WBE range is 50–65% [36,37]. In the IEC system, humidity (g/kg of dry air DA) of inlet air and outlet air remains the same. However, enthalpy (kJ/kg of dry air DA) of outlet air is decreased [1]. Schematic and psychrometric representation Appl. Sci. 2020, 10, 4445 6 of 18 of the IEC system is shown in Figure4b. Further insights into the IEC system are governed by Equations (4)–(7) given in the literature [3].

(DBT) (WBT) (4) outlet ≥ inlet

(RH)outlet > (RH)inlet (5)

woutlet = winlet (6)

houtlet < hinlet (7) where w and h represent the humidity ratio (kg/kg) and enthalpy of air (kJ/kg), and subscripts outlet and inlet represent outlet and inlet air conditions, respectively.

3.1.3. Maisotsenko-Cycle EC (MEC) System Maisotsenko-cycle evaporative cooling (MEC) is the system in which ambient air undergoes a thermodynamic process in which psychrometric renewable energy available from the air is utilized to reduce the temperature of ambient air [1,38,39]. It is also called an advanced IEC system or regenerative evaporative cooling system [40]. In the MEC system, the cooling eﬀect is produced by two thermodynamic processes: evaporative cooling and heat transfer [1,41] in which temperature of ambient air nearly reaches the dewpoint temperature instead of wet-bulb temperature [16,39,42]. It consists of three channels: one wet channel and two dry channels. The wet channel is sandwiched between two dry channels. When ambient air passes through the dry channel, it becomes cool due to convective heat transfer between wet and dry channels. In the MEC system, humidity (g/kg of dry air DA) of inlet air and outlet air remains the same. However, enthalpy (kJ/kg of dry air DA) of outlet air decreases [33,36]. Schematic and psychrometric representation of the MEC system is shown in Figure4c. Further insights into the MEC system are governed by Equations (8)–(11) given in the literature [3]. (DPT) (DBT) (WBT) (8) inlet ≤ outlet ≤ inlet

(RH)outlet > (RH)inlet (9)

woutlet = winlet (10)

houtlet < hinlet (11) where DPT, DBT, and WBT represent dewpoint, dry-bulb, and wet-bulb temperatures (◦C), respectively, RH represents relative humidity (%), w and h represent the humidity ratio of air (kg/kg) and enthalpy of air (kJ/kg), respectively, and subscripts outlet and inlet represent outlet and inlet air conditions, respectively. Performance of the EC systems can be assessed in terms of their eﬀectiveness, i.e., wet-bulb eﬀectiveness (WBE), given by Equation (12).

DBT DBT E = inlet − outlet (12) WB DBT WBT inlet − inlet where εWB, DBT, and WBT represent wet-bulb eﬀectiveness (-), dry-bulb and wet-bulb temperatures of air (◦C), respectively, and the subscripts inlet and outlet represent inlet and outlet air conditions, respectively.

3.2. Research Methodology To determine the design cooling load for the AC system, heat produced (HP) by the birds and their THI is required. Pedersen (2000) [43,44] model is used to calculate the HP (sensible and latent) per bird for climatic conditions of Multan. Figure5 represents an illustration of integration of EC systems into a poultry house and sensible and latent heat load generated by a poultry bird. Heat production in birds Appl. Sci. 2020, 10, x FOR PEER REVIEW 7 of 18

퐻푃 = 60.64 + 0.04퐿푊 (13) where HP represents heat production from poultry birds (W/kg) and LW represents the live weight of poultry birds (g). Sensible and latent heat production per bird is calculated using the Pedersen (2000) model given by Equations (14) and (15), respectively [43,44].

3 −5 3 푄푡 = 9.84푚푎(4. 10 (20 − 푇푑푏) + 1) (14)

−7 4 푄푠 = 0.83푄푡(0.8 − 1.85푒 (푇푑푏 + 10) ) (15) where Qt and Qs represent total and sensible heat productions (J/s), respectively, and ma represents the mass of live birds (kg) and Tdb represents dry-bulb temperature (°C). The temperature-humidity index (THI) is a linear combination of dry-bulb temperature and wet- bulb temperature. THI has been established to evaluate the effect of the thermal environment on thermoregulatory status of poultry birds [47]. Equation (16) governs THI for broilers [47].

푇퐻퐼 = 0.85푇푑푏 + 0.15푇푤푏 (16) where THI represents temperature-humidity index (°C), and Twb represents wet-bulb temperature of air (°C ). The wet-bulb temperature for poultry birds is calculated by Equation (17) [48,49]. 1 −1 −1 푇푤푏 = 푇푑푏푡푎푛 [0.151977 + (푅퐻 + 8.313659)2 ] + 푡푎푛 (푇푑푏 + 푅퐻) 3 (17) − 푡푎푛−1(푅퐻 − 1.676331) + 0.00391838 푅퐻2푡푎푛−1(0.023101 푅퐻) − 4.686035 where RH represents relative humidity of air (%). THI has been developed based on body temperature responses instead of production responses

[47]Appl.. Sci.Based2020 ,on10, physiological 4445 parameters such as: body temperature, respiration rate, or pulse 7rate, of 18 heat production, or production performance, THI equations describe the importance of Tdb and Twb for a range of animals including poultry birds and cattle [50]. However, THI fails to integrate the effechangesct of air with velocity respect (V to) theiron animal body thermal weight [45comfort]. The [50] birds. E growffects musclesof air velocity over time on body due to temperature consuming ofmore poultry energy birds produced is accounted from feedfor by intake integrating [46]. As V a into result, THI more [27]. heat Due is to released. the nonlinear Heat productionnature of V, ( HPthe) asymptoticalin poultry birds function is governed is considered by Equation [50] (13). Consequently, given in the literaturethe temperature [26]. -humidity-velocity index (THVI) is used in this study for homeostasis (i.e., ability of an animal to maintain constant internal conditions in the face of fluctuating externalHP = conditions)60.64 + 0.04 ofLW birds [27]. With increase in velocity up(13) to a certain point (i.e., 1.2 m/s), optimum thermal comfort for poultry birds inside a poultry can be where HP represents heat production from poultry birds (W/kg) and LW represents the live weight of achieved [50]. THVI is calculated by Equation (18) given in the literature [27]. poultry birds (g). 푇퐻푉퐼 = 푉−0.058 푇퐻퐼 (18)

solar radiation

respiration sensible heat heat fan T RH T RH DEC/IEC or MEC system latent hot cold metabolic heat exhaustair ambient air supply air heat

Figure 5. SchemeScheme of of temperature temperature and and humidity humidity control control system(s) system(s) in in a a typical typical poultry poultry shed shed for maintaining the thermal comfort of poultry birds.

Sensible and latent heat production per bird is calculated using the Pedersen (2000) model given by Equations (14) and (15), respectively [43,44].

3 5 3 Qt = 9.84m (4.10− (20 T ) + 1) (14) a − db 7 4 Qs = 0.83Qt(0.8 1.85e− (T + 10) ) (15) − db where Qt and Qs represent total and sensible heat productions (J/s), respectively, and ma represents the mass of live birds (kg) and Tdb represents dry-bulb temperature (◦C). The temperature-humidity index (THI) is a linear combination of dry-bulb temperature and wet-bulb temperature. THI has been established to evaluate the eﬀect of the thermal environment on thermoregulatory status of poultry birds [47]. Equation (16) governs THI for broilers [47].

THI = 0.85Tdb + 0.15Twb (16) where THI represents temperature-humidity index (◦C), and Twb represents wet-bulb temperature of air (◦C). The wet-bulb temperature for poultry birds is calculated by Equation (17) [48,49].

1 1 1 Twb = Tdbtan− 0.151977 + (RH + 8.313659) 2 + tan− (Tdb + RH) 1 3 1 (17) tan (RH 1.676331) + 0.00391838 RH 2 tan (0.023101 RH) − − − − 4.686035 − where RH represents relative humidity of air (%). THI has been developed based on body temperature responses instead of production responses [47]. Based on physiological parameters such as: body temperature, respiration rate, or pulse rate, heat production, or production performance, THI equations describe the importance of Tdb and Twb for a Appl. Sci. 2020, 10, x FOR PEER REVIEW 8 of 18

4. Results and Discussion Appl. Sci. 2020, 10, 4445 8 of 18 The results from the developed EC systems are obtained for the climatic conditions of Multan (Pakistan), which are presented in Figure 6. Ambient air temperature ranges from 12.3 °C to 42.1 °C. rangeThe DEC of animals system includingresulted in poultry a temperature birds and range cattle of [50 10]. °C However, to 32.3 THI°C, which fails to created integrate a temperature the effect of airgradient velocity of (10.9V) on °C. animal The IEC thermal system comfort resulted [50 in]. Eaff temperatureects of air velocity range onof 10.8 body °C temperature to 35.5 °C, ofwhich poultry led birdsto a temperature is accounted gradient for by integrating (i.e., difference V into between THI [27 ].ambient Due to and the nonlinearsupply air nature temperature) of V, the of asymptotical 7.4 °C. The functionMEC system is considered resulted [50 in ]. a Consequently, temperature range the temperature-humidity-velocity of 13.2 °C to 31.6 °C, which index created (THVI) the maximum is used in thistemperature study for gradient homeostasis of 14.4 (i.e., °C. abilityFrom these of an results, animal the to MEC maintain system constant performs internal better conditions when compared in the faceto the of DEC fluctuating and IEC external systems conditions) in terms of ofthe birds temperature [27]. With gradient. increase The in trend velocity of relative up to a humidity certain point (%) (i.e.,of ambient 1.2 m/s) air,, optimum DEC, IEC thermal, and MEC comfort systems for poultry is also birds presented inside ain poultry Figure can 6. The be achieved DEC, IEC, [50 ].and THVI MEC is calculatedsystems resulted by Equation in relative (18) givenhumidity in the ranging literature from [27 72%]. to 98%, 51% to 78.5%, and 66.7% to 93.6%, respectively. A maximum increase in relative humidity is observed in case of the DEC system as THVI = V 0.058 THI (18) compared to IEC and MEC systems. Additionally, −Figure 6 shows that April to June are hot and dry 4.months Results whereas and Discussion July to October are hot and humid months, which indicated a need for AC in both. Figure 7 shows performance of the EC systems based on wet-bulb effectiveness for DEC, IEC, and MECThe systems results. The from DEC the and developed MEC systems EC systems resulted are in obtainedrelatively for higher the climaticeffectiveness conditions when ofcompared Multan (Pakistan),to the IEC system. which are MEC presented system achieved in Figure 6maximum. Ambient effectiveness air temperature of 0.98 ranges in November. from 12.3 Additionally,◦C to 42.1 ◦C. TheDEC DEC and systemIEC systems resulted achieved in a temperature maximum wet range-bulb of effectiveness 10 ◦C to 32.3 of◦C, 0.96 which and created0.57 in September a temperature and gradientMay, respectively. of 10.9 ◦C. The IEC system resulted in a temperature range of 10.8 ◦C to 35.5 ◦C, which led to a temperatureFigure 8 represents gradient the (i.e., relationship difference of between heat production ambient and(HP) supply and temperature air temperature)-humidity of 7.4 index◦C. The(THI MEC) with system live weight resulted of poultry in a temperature birds. HP rangeof poultry of 13.2 birds◦C toincrease 31.6 ◦C,s in which linear created function the with maximum respect temperatureto LW. In the gradient early stage of 14.4 of◦ C.poultry From thesegrowth, results, higher the MECTHI is system tolerated performs while better justifyin wheng the compared earlier tostatement the DEC about and IEC use systems of heaters in terms for one of- theweek temperature old chicks gradient.. Heat production The trend is of at relative peak w humidityhen poultry (%) ofbirds ambient achieve air, harvest DEC, IEC,mass and. Poultry MEC birds systems ready is also for harvest presented generate in Figure the6 highest. The DEC, heat IEC,(i.e., and171 W/m MEC2) systemsagainst THI resulted of 18.2 in °C relative at 2.75 humidity-kg live weight. ranging from 72% to 98%, 51% to 78.5%, and 66.7% to 93.6%, respectively. A maximum increase in relative humidity is observed in case of the DEC system as Figure 9 shows the relation of relative humidity and THI with reference to Tdb. Increase in comparedhumidity up to to IEC the and optimal MEC value systems. of dry Additionally,-bulb temperature Figure6 works shows accordingly that April toto Juneovercome are hot heat and stress. dry months whereas July to October are hot and humid months, which indicated a need for AC in both. Figure 10 represents the effect of Tdb on THVI with respect to varying air velocity. It is noticed that, Figure7 shows performance of the EC systems based on wet-bulb e ffectiveness for DEC, IEC, and at a fixed value of Tdb, THVI decreases slightly with an increase in the velocity of air. Moreover, Figure MEC11 shows systems. THI Thewith DEC a varying and MEC temperature systems resulted and relative in relatively humidity. higher THI e ffrangesectiveness from when 28 °C compared to 30 °C, towhich the IEC indicates system. an MECalarming system situation achieved for maximumthe poultry e ffbirdsectiveness. It turns of into 0.98 a in dangerous November. situation Additionally, when DECTHI surpasses and IEC systems 30 °C. An achieved emergency maximum action is wet-bulb required e ffifectiveness the THI value of 0.96 surpasses and 0.57 31 in °C. September Poultry birds and May,grow respectively.healthier at 18 °C to 29 °C and 50% RH [47].

Temp_ambient Temp_IEC Temp_DEC Temp_MEC

RH_IEC RH_DEC RH_MEC RH_ambient 45 100 40 90 35

80 C)

30 70 25

20 60 Temperature ( Temperature

15 50 Relative humidity (%)

10 40

5 30 1 2 3 4 5 6 7 8 9 10 11 12 Months Figure 6.6. The annual proﬁlesprofiles of temperature and relative humidity for ambient conditions of Multan and outputoutput conditionsconditions ofof thethe DEC,DEC, IEC,IEC, andand MECMEC systems.systems. Appl. Sci. 2020, 10, 4445 9 of 18 Appl. Sci. 2020, 10, x FOR PEER REVIEW 9 of 18

Ɛwb_IEC Ɛwb_DEC Ɛwb_M-Cycle 1 Yearly analysis 0.8

Appl. Sci. 20) 20, 10, x FOR PEER REVIEW 9 of 18 -

0.6 Ɛwb_IEC Ɛwb_DEC Ɛwb_M-Cycle 1 Yearly

Effectiveness ( Effectiveness 0.4 analysis

0.8

) - 0.2 0.6 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Months

Figure 7. TheThe achieved achieved wet wet-bulb-bulb effectiveness eﬀectiveness of of the EC systems against the results presented in Effectiveness ( Effectiveness 0.4 Figure6 6 for for climaticclimatic conditionsconditions ofof Multan.Multan.

Figure2008 represents the relationship of heat production (HP) and temperature-humidity31 index (THI) with0.2 live weight ofTemperature poultry birds. HPhumidity of poultry index birds increases( C) in linear function with respect to LW. In the earlyJan stage ofFeb poultryMar growth,Apr higherMay THIJun is toleratedJul Aug whileSep justifyingOct theNov earlierDec statement

180 29 C)

about use of heaters for one-week old chicks. HeatMonths production is at peak when poultry birds achieve )

harvest mass.2 Poultry birds ready for harvest generate the highest heat (i.e., 171 W/m2) against THI of Figure 160 7. The achieved wet-bulb effectiveness of the EC systems against the results presented27 in 18.2 C at 2.75-kg live weight. Figure◦ 6 for climatic conditions of Multan. 140 25 200 31 120 Temperature humidity index ( C) 23

180 29 C)

100 21 ) 2 160 27

80 19 Heat Heat production(W/m 140 2 25

60 Heat production (W/m ) 17 Temperature humidity ( index Temperature 120 23 40 15 100 0 500 1000 1500 2000 2500 300021 Weight of bird (g)

80 19 Heat Heat production(W/m Figure 8. The variations of heat production and THI with2 respect to weight of poultry birds.

60 Heat production (W/m ) 17 Temperature humidity ( index Temperature Sensible and latent HP per bird directly effects their mortality rate. It also explains the complex situation of40 heat stress gained by poultry birds. As the ambient temperature starts increasing,15 HP per bird gets increased.0 Moreover,500 there1000 remains a1500 widening2000 gap between2500 the values3000 of sensible and latent heat production per bird. Once this gap gets shrieked under any abnormal condition of ambient temperature, there comes an end to theWeight welfare ofof poultry bird (g) birds. Figure 12 represents the variations in heat production against the weight of poultry birds at different temperatures. FigureFigure 8. 8. TheThe variations variations of of heat heat production production and and THI THI with with respect respect to to weight weight of of poultry poultry birds. birds.

Sensible and latent HP per bird directly effects their mortality rate. It also explains the complex situation of heat stress gained by poultry birds. As the ambient temperature starts increasing, HP per bird gets increased. Moreover, there remains a widening gap between the values of sensible and latent heat production per bird. Once this gap gets shrieked under any abnormal condition of ambient temperature, there comes an end to the welfare of poultry birds. Figure 12 represents the variations in heat production against the weight of poultry birds at different temperatures. Appl. Sci. 2020, 10, 4445 10 of 18

Figure9 shows the relation of relative humidity and THI with reference to Tdb. Increase in humidity up to the optimal value of dry-bulb temperature works accordingly to overcome heat stress. Figure 10 represents the eﬀect of Tdb on THVI with respect to varying air velocity. It is noticed that, at a ﬁxed value of Tdb, THVI decreases slightly with an increase in the velocity of air. Moreover, Figure 11 shows THI with a varying temperature and relative humidity. THI ranges from 28 ◦C to 30 ◦C, which indicates an alarming situation for the poultry birds. It turns into a dangerous situation when THI surpasses 30 ◦C. An emergency action is required if the THI value surpasses 31 ◦C. Poultry birds grow Appl. Sci. 2020, 10, x FOR PEER REVIEW 10 of 18 Appl.healthier Sci. 2020 at, 10 18, x◦ CFOR to PEER 29 ◦C REVIEW and 50% RH [47]. 10 of 18 40

C) C)

35 35 Tdb 36 ( C) Tdb 36 ( C) 34 ( C) 34 ( C) 30 32 ( C) 30 32 ( C) 30 ( C) 30 ( C)

humidity index ( index humidity 28 ( C) -

humidity index ( index humidity 25 28 ( C)

- 26 ( C) 25 26 ( C) 24 ( C) 24 ( C) 22 ( C) 20 22 ( C) 20 20 ( C)

Temperature 20 ( C) 18 ( C)

Temperature 18 ( C) 15 15 10 20 30 40 50 60 70 80 90 10 20 30 40 50 60 70 80 90 Relative humidity (%) Relative humidity (%)

Figure 9. The optimum thermal comfort requirements of the poultry birds of different ages. FigureFigure 9. 9. TheThe optimum optimum thermal thermal comfort comfort requirements requirements of of the the poultry poultry birds birds of of different diﬀerent age ages.s.

40 40

Tdb 36 ( C) 35 Tdb 36 ( C) 35 34 ( C) 32 ( C) 34 ( C)

velocity index index velocity 32 ( C)

- 30 30 ( C) velocity index index velocity

- 30 30 ( C)

28 ( C)

C) C)

( 28 ( C) C) C)

26 ( C)

( 25

humidity 26 ( C)

- 25 24 ( C) humidity - 24 ( C) 22 ( C) 20 20 ( C) 22 ( C) 20 20 ( C) 18 ( C)

18 ( C) Temperature

Temperature 15 15 0.2 0.4 0.6 0.8 1 0.2 0.4 Velocity0.6 (m/sec) 0.8 1 Velocity (m/sec)

Figure 10. The variation of THVI as a function of air velocity at diﬀerent Tdb. Figure 10. The variation of THVI as a function of air velocity at different Tdb. Figure 10. The variation of THVI as a function of air velocity at different Tdb. Figure 12(a) shows an increase in total HP by poultry birds since they gain weight at 18 °C. At an earlyFigure stage, 12(a) sensibleshows an HP increase increases in total comparatively HP by poultry higher birds than since that they of gain latent weight HP. at This 18 °C. trend At ancontinues early stage,to grow. sensible It is seen HP that, increases at 3 kg weight comparatively of poultry higher bird, sensible than that HP of(i.e. latent, 14.8 W/kg) HP. This is roughly trend continuesdouble the to value grow. of It latentis seen HP that, (i.e. at, 3 7.5 kg W/kg).weight Similarly,of poultry bird,Figure sensible 12(b)-12 HP(d) (i.e. shows, 14.8 theW/kg) trend is roughly of total doubleHP by poultrythe value birds of latent of different HP (i.e. live, 7.5 weight W/kg).s atSimilarly, 30 °C, 40 Figure °C, and 12(b) 45 -°C,12(d) respectively. shows the Sensibletrend of (13.7total HPW/kg) by andpoultry latent birds (7.7 ofW/kg) different HP is live observed weight ats 30at 30°C. °C, Sensible 40 °C, and and latent 45 °C, HP respectively. of 6.9 W/kg Sensible and 8.1 W/kg (13.7 W/kg)as well and as 3.4 latent W/kg (7.7 and W/kg) 4.5 W/kg HP is at observed 40 °C and at 45 30 °C, °C. respectively. Sensible and Additionally, latent HP of 6.9 Figure W/kg 12(d) and indicates8.1 W/kg asa higher well as latent 3.4 W/kg HP comparedand 4.5 W/kg to sensible at 40 °C HPand indicating 45 °C, respectively. that the bird Additionally, is suffocating Figure due 12(d) to an indicates increase ain higher the humidity latent HP ratio compared in the surrounding to sensible HPair. indicatingMoreover, thatat 40 the °C, bird the isdiff suffocatingerence between due to sensible an increase and inlatent the humidityHP is at theratio lowest in the, surroundingwhich indicates air. Moreover,that the bird at 40is °C,about the to diff expireerence due between to heat sensible stress and latentsuffocation. HP is Withat the increasing lowest, which THI, poultry indicates birds that start the losingbird is their about strength to expire to fight due againstto heat heatstress stress. and suffocation. With increasing THI, poultry birds start losing their strength to fight against heat stress. Impact of Tdb and Twb on THI is further explored in Appendix A, as given by Figure A1. Impact of Tdb and Twb on THI is further explored in Appendix A, as given by Figure A1. Appl. Sci. 2020, 10, 4445 11 of 18 Appl. Sci. 2020, 10, x FOR PEER REVIEW 11 of 18

Figure 11. TThehe numerical values of THI corresponding to various temperature and relative humidity levels. The The green color presents relatively better THI whereas a red color reﬂectsreflects the worst scenario of THI.THI.

Sensible and latent HP per bird directly eﬀects their mortality rate. It also explains the complex (a) 25 (b) 25 situation of heatTotal stressheat gainedT= 18 byC poultry birds. As the ambientTotal temperature heat startsT= 30 increasing, C HP per 20 20 bird gets increased.Latent heat Moreover, there remains a widening gap betweenLatent heat the values of sensible and latent heat15 productionSensible per heat bird. Once this gap gets shrieked15 underSensible any heat abnormal condition of ambient temperature, there comes an end to the welfare of poultry birds. Figure 12 represents the variations in 10 10 heat production against the weight of poultry birds at diﬀerent temperatures.

Figure5 12a shows an increase in total HP by poultry5 birds since they gain weight at 18 ◦C. At an Total heat heat production (W/kg) Total early heat production (W/kg) Total stage, sensible HP increases comparatively higher than that of latent HP. This trend continues to 0 0 grow. It0 is seen0.5 that,1 at 31.5 kg weight2 of2.5 poultry3 bird, sensible0 HP0.5 (i.e.,1 14.81.5 W/kg)2 is roughly2.5 double3 the value of latent HPLive (i.e., weight 7.5 (kg) W/kg). Similarly, Figure 12b–d shows theLive trend weight of (kg) total HP by poultry (c) 9 16 (d) birds of different live weights at 30 ◦C, 40 ◦C, and 458 ◦C, respectively.Total heat SensibleT= 45 C (13.7 W/kg) and 14 Total heat T= 40 C latent (7.7 W/kg) HP is observed at 30 ◦C. Sensible and7 latent HPLatent of heat 6.9 W/kg and 8.1 W/kg as well as 12 Latent heat 6 3.4 W/kg and 4.5 W/kg at 40 ◦C and 45 ◦C, respectively. Additionally, Figure 12d indicates a higher 10 Sensible heat Sensible heat latent HP compared to sensible HP indicating that the5 bird is suffocating due to an increase in the 8 4 humidity6 ratio in the surrounding air. Moreover, at 403◦C, the difference between sensible and latent HP is4 at the lowest, which indicates that the bird is about2 to expire due to heat stress and suffocation. 1 2 heat production(W/kg) Total

With heat production(W/kg) Total increasing THI, poultry birds start losing their strength to ﬁght against heat stress. Impact of Tdb 0 and T0 on THI is further explored in AppendixA, as given by Figure A1. wb0 0.5 1 1.5 2 2.5 3 0 0.5 1 1.5 2 2.5 3 Figure 13 shows yearlyLive weight THI (kg) analysis of ambient air under DEC, IEC, andLive MECweight (kg) systems. Permissible limit of THI denotes 30 ◦C Tdb and 50% RH. THI of ambient air from November to March (winter) is withinFigure the 12. permissible The sensible limit,and latent which heat indicates production no per need poultry of AC bird for for poultry (a) 18 °C, birds. (b) 30 Figure°C, (c) 40 14 °C, shows a psychrometricand (d) 45 °C. representation of performance variation of EC systems from April to October for the climatic conditions of Multan against thermal comfort zones of poultry birds of diﬀerent ages.

Appl. Sci. 2020, 10, x FOR PEER REVIEW 11 of 18

Appl. Sci. 2020, 10, 4445 12 of 18

The detailed psychrometric representation of the EC systems performance for the months of April to October is provided in AppendixA, as given by Figure A2a–g, respectively. Results indicate that MEC, DEC,Figure and IEC 11. systemsThe numerical somewhat values achieveof THI corresponding required thermal to various comfort temperature conditions and relative of diﬀerent humidity ages of the poultrylevels. forThe somegreen ofcolor the presents months relatively (April to better October). THI whereas Moreover, a red applicability color reflects ofthe the worst EC systemsscenario for poultryof ACTHI. and ventilation from the viewpoint of THI is summarized in Table1.

(a) 25 (b) 25 Total heat T= 18 C Total heat T= 30 C 20 20 Latent heat Latent heat 15 Sensible heat 15 Sensible heat

10 10

5 5

Total heat heat production (W/kg) Total Total heat heat production (W/kg) Total 0 0 0 0.5 1 1.5 2 2.5 3 0 0.5 1 1.5 2 2.5 3 Live weight (kg) Live weight (kg) (c) 9 16 (d) 8 Total heat T= 45 C Appl. Sci.14 2020, 10Total, x FOR heat PEER REVIEWT= 40 C 12 of 18 7 Latent heat 12 Latent heat 6 Figure 13 shows yearly THI analysis of ambient air underSensible DEC,heat IEC, and MEC systems. 10 Sensible heat 5 Permis8sible limit of THI denotes 30 °C Tdb and 50% RH.4 THI of ambient air from November to March (winter)6 is within the permissible limit, which indicates3 no need of AC for poultry birds. Figure 14 shows4 a psychrometric representation of performance variation2 of EC systems from April to October 1 2 heat production(W/kg) Total for the heat production(W/kg) Total climatic conditions of Multan against thermal comfort zones of poultry birds of different ages. 0 0 The detail0 ed psychrometric0.5 1 1.5 representation2 2.5 of3 the EC systems0 performance0.5 1 for1.5 the month2 s2.5 of April3 to Live weight (kg) Live weight (kg) October is provided in Appendix A, as given by Figure A2 (a)-(g), respectively. Results indicate that MEC, DEC, and IEC systems somewhat achieve required thermal comfort conditions of different ages Figure 12. The sensible and latent heat production per poultry bird for (a) 18 C, (b) 30 C, (c) 40 C, of theFigure poultry 12. for The some sensible of theand months latent heat (April production to October). per poultry Moreover, bird for applicability (a) 18◦ °C, (b) of30◦ °C,the (ECc) 40 systems◦ °C, and (d) 45 ◦C. for poultryand (d AC) 45 °Cand. ventilation from the viewpoint of THI is summarized in Table 1. THI of ambient air THI of IEC product air

THI of DEC product air THI of MEC product air

45 C) Yearly analysis 40 Permissible limit 35 30 25 20 15 10

Temperature humidity ( index Temperature 5 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Months Figure 13. AnnualAnnual profile proﬁle of of THI THI resulting resulting from from the the EC EC system systemss for forclimatic climatic conditions conditions of Multan. of Multan. The Thered dotted red dotted line lineshows shows the optimum the optimum level level of THI of THIi.e., i.e.,30. 30.

Figure 14. Psychrometric representation of the performances of EC systems for the months of April to October. Appl. Sci. 2020, 10, x FOR PEER REVIEW 12 of 18

Figure 13 shows yearly THI analysis of ambient air under DEC, IEC, and MEC systems. Permissible limit of THI denotes 30 °C Tdb and 50% RH. THI of ambient air from November to March (winter) is within the permissible limit, which indicates no need of AC for poultry birds. Figure 14 shows a psychrometric representation of performance variation of EC systems from April to October for the climatic conditions of Multan against thermal comfort zones of poultry birds of different ages. The detailed psychrometric representation of the EC systems performance for the months of April to October is provided in Appendix A, as given by Figure A2 (a)-(g), respectively. Results indicate that MEC, DEC, and IEC systems somewhat achieve required thermal comfort conditions of different ages of the poultry for some of the months (April to October). Moreover, applicability of the EC systems for poultry AC and ventilation from the viewpoint of THI is summarized in Table 1. THI of ambient air THI of IEC product air THI of DEC product air THI of MEC product air

45 C) Yearly analysis 40 Permissible limit 35 30 25 20 15 10

Temperature humidity ( index Temperature 5 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Months Appl. Sci.Figure2020, 10 13., 4445 Annual profile of THI resulting from the EC systems for climatic conditions of Multan. The 13 of 18 red dotted line shows the optimum level of THI i.e., 30.

FigureFigure 14. 14.Psychrometric Psychrometric representation representation ofof thethe performancesperformances of of EC EC systems systems for for the the months months of ofApril April to October.to October.

Table 1. Applicability/feasibility of the EC systems for the climatic conditions of Multan. The results are based on numerical values of THI.

Months Ambient Conditions DEC IEC MEC January √ √ √ √ February √ √ √ √ March √ √ √ √ April √ √ √ × May √ √ × × June × × × × July × × × × August √ × × × September √ √ × × October √ √ √ × November √ √ √ √ December √ √ √ √

5. Conclusions This study is aimed to analyze the performance of low-cost evaporative cooling (EC) options for climatic conditions of Multan (Pakistan). The hot and dry summer of Multan demands an eﬃcient air-conditioning (AC) system for poultry birds. In this regard, the EC systems can provide cost-eﬀective and an environmentally-friendly solution. Therefore, three kinds of EC systems, i.e., direct EC (DEC), indirect EC (IEC), and Maisotsenko-cycle EC (MEC) are investigated for thermal comfort of poultry birds. Thermal comfort of poultry birds in each case of the EC systems was assessed in terms of temperature-humidity (THI) and temperature-humidity-velocity (THVI) indices. Heat production against age and weight of poultry birds was also investigated. Weight of poultry birds with growing age increases. Consequently, heat production is also increased. This increased value of heat production (HP) gives birth to heat stress for growing birds. Young birds with less weight can survive a slightly higher range of THI compared to older birds, which show immense signs of heat stress with increasing weight. At ambient temperature higher than or equal to the normal poultry body temperature, latent Appl. Sci. 2020, 10, 4445 14 of 18

HP surpasses sensible HP, which causes suffocation due to an increased latent load in the ambient air. DEC, IEC, and MEC systems achieve the required thermal comfort sensation for poultry birds. However, the DEC system increases relative humidity up to such an extent that it causes suffocation for the birds. It is concluded that, in summer conditions (with Tdb > 40 ◦C) when poultry birds attain harvest mass, their heat production results in a higher latent load into the ambient air. Since the EC systems also contribute latent load into the supply air, poultry birds face suffocation due to excessive humidity in the air, which can be controlled by developing hybrid combinations of VCAC-EC systems. Additionally, MEC coupled with a desiccant air-conditioning unit (M-DAC) could potentially achieve thermal comfort of poultry birds for all months across Pakistan.

Author Contributions: Conceptualization, H.M.U.R. and M.S. Methodology, H.M.U.R. and H.A. Software, H.M.U.R. and H.A. Validation, M.S. and T.M. Formal analysis, H.M.U.R., H.A., and K.S. Investigation, M.S. and T.M. Resources, M.S. and M.U. Data curation, H.M.U.R., H.A., K.S., and R.R.S. Writing—original draft preparation, H.M.U.R. Writing—review and editing, M.S., T.M., M.U., R.R.S., Y.Z., and R.A. Visualization, M.S., M.U., R.R.S., Y.Z., and R.A. Supervision, M.S. and T.M. Project administration, M.S. Funding acquisition, M.S. All authors have read and agreed to the published version of the manuscript. Funding: This research received no external funding. Acknowledgments: All this work is part of the Ph.D. research of Hafiz Muhammad Umar Raza (1st Author). This research work has been carried out in the Department of Agricultural Engineering, Bahauddin Zakariya University,Appl. Sci. 2020 Multan-Pakistan., 10, x FOR PEER REVIEW The Bahauddin Zakariya University, Multan-Pakistan under the14 Directorof 18 Research/ORIC grant titled “Development and performance evaluation of prototypes of direct and indirect evaporativeevaporative cooling-based cooling-based air air-conditioning-conditioning systems”, systems”, awarded awarded to Principal to Principal Investigator Investigator Dr. Muhammad Muhammad Sultan Sultan,, fundedfunded this this research. research We. We acknowledge acknowledge support support for the for Open the Open Access Access fees by fees the by Hamburg the Hamburg University University of Technology of (TUHH)Technology in the (TUHH) funding in programme the funding Openprogramme Access Open Publishing. Access Publishing. Conflicts of Interest: The authors declare no conflict of interest. Conflicts of Interest: The authors declare no conflict of interest. Appendix A Appendix A

Figure A1. Impact of Tdb and Twb on THI for the EC systems represented on contour plots. Figure A1. Impact of Tdb and Twb on THI for the EC systems represented on contour plots. Appl. Sci. 2020, 10, 4445 15 of 18 Appl. Sci. 2020, 10, x FOR PEER REVIEW 15 of 18

FigureFigure A2. A2.Psychrometric Psychrometric representation representation of theof the performances performances of ECof EC systems systems for for the the months months of (ofa) April,(a) (b)April, May, ((cb)) June, May, ((dc) June, July, ((ed)) August,July, (e) August, (f) September, (f) September, and (g) and October. (g) October.

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