Characteristics Study of Two-Stage Cascade Refrigeration System Design for Household Air Blast Freezing

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International Journal of Mechanical Engineering and Technology (IJMET) Volume 10, Issue 01, January 2019, pp. 1804-1813, Article ID: IJMET_10_01_178 Available online at http://iaeme.com/Home/issue/IJMET?Volume=10&Issue=1 ISSN Print: 0976-6340 and ISSN Online: 0976-6359

CHARACTERISTICS STUDY OF TWO-STAGE CASCADE REFRIGERATION SYSTEM DESIGN FOR HOUSEHOLD AIR BLAST FREEZING

Darwin R.B Syaka, I Wayan Sugita and Muhammad Bijaksana Department Mechanical and Vocational Education State University of Jakarta, Gedung B Kampus Rawamangun Jl. Rawamangun Muka, Jakarta, Indonesia, 13220

ABSTRAK The major problem of archipelago communities is the storage of seafood that depends on a particular season. In order for seafood to be preserved for long periods of time then, it should be frozen using air blast freezing. However, the existing air blast freezing is still on an i ndustrial s cale. Ther efore, t he ai m of t his s tudy i s s imulation of t he two-stage cascade refrigeration system model, validation and evaluation of the model with experiment dat a. Thi s r esearch w as pr eceded by a des ign f or t he t wo s tage cascade refrigeration system R22/R32 followed by experiment to obtain operational parameters which will then be validated and evaluated of the components of this cascade refrigeration system. The r esults of t his r esearch ar e des ign, oper ational and anal ysis m ethods to determine par ameters and s pecifications of ai r bl ast f reezing com ponents including: pressure of system, cooling temperature, compressor power required, cooling load and evaluation required for its performance to be better Keywords: Air Blast Freezing, Cascade Refrigeration System, Design, Evaluation Cite this Article: Darwin R.B Syaka, I Wayan Sugita and Muhammad Bijaksana, Characteristics Study of Two-Stage Cascade Refrigeration System Design for Household Air B last Fr eezing, I nternational J ournal of M echanical E ngineering and Technology, 10(01), 2019, pp.1804–1813 http://iaeme.com/Home/issue/IJMET?Volume=10&Issue=1 1. INTRODUCTION To improve the economy of the archipelago communities has various problems, such as: capital, unstable productivity, and various other things. And the most specific thing that usually becomes the main problem is the storage of marine products that are still dependent on those that exist in certain seasons. The main results of the archipelago communities are generally fish-based, which is known, that the fish is easily damaged (rot), and only able to survive about 8 hours after the arrest. The caus es of fish qui ckly decom pose, among others, due to m icroorganisms, s uch as bacteria and fungi[1]. Commonly used storage / preservation methods are basically divided into 4 groups, i.e. 1) using physical factors, 2) preservatives, 3) utilizing physical factors and

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preservatives, and 4) fermentation. But for further processing, fish preservation should be done without changi ng t he t exture / s hape, t aste, and s mell of f ish. So t he bes t pr ocess i s t o take advantage of physical factors, and physical factors that mean using low temperatures because the advantage of using low temperatures will make the material in durable does not change the texture / shape, taste, and smell[1]. Commonly us ed l ow t emperature pr eservation m ethods ar e f reezing, ai r bl ast f reezing or cryogenic. Comparative study of the 3 methods was performed by M. Bueno, et al. [2]states that after being stored for 10 months, the method of air blast freezing has the quality of the meat closest to fresh meat. Similar research conducted by E. Muela, et al. [3] also supports the result that the method of preservation with air blast freezing at the final temperature of pruduk -18˚C has the meat quality closest to fresh meat after being stored for 1, 3 and 6 months. This occurs because t he method of fast freezing (blast f reezing) offers a new technique for disrupting microbial cells[4] and with this method the recovery is relatively higher than that obtained by other m ethods[5]. A s f or t he m arine pr oducts s hould be cooled t o t he f inal t emperature of - 15˚C[6]. Although the results of the preservation study on the fillet quality of catfish species with cryogenic method were better than the air blast freezing method but the quality did not differ significantly[7] but, compared with the 3 preservation methods at ot her low temperatures, cryogenic method the highest investment and operational costs[8], therefore the method of air blast f reezing i s a p referred m ethod of pr eserving m arine pr oducts s uitable f or archipelago communities. Air blast freezing is a cooling technique by utilizing air to keep the temperature inside the cooling room so that the inside temperature of the cooling room remains stable and there is no temperature rise in the cooling room[9]. Air blast freezing has flexibility because the air on the fan can overcome various forms of irregular product and various sizes besides that exhaled air causes uniform temperature in the cabin room so that cooling can take place evenly. Freezing with ai r bl ast f reezing depends on t he ai r v elocity and t he pr eparation of t he r ack s o that circulation can be well circulated then the temperature will quickly cool to produce the optimum temperature f or cooli ng t he pr oduct. T he advant ages of t he ai r bl ast f reezing m ethod ar e the flexibility and low capital cost[10] however, the existing blast freezer water cooler in the market is now still in industrial scale, making it expensive and large in size, therefore air blast freezing is not suitable for remote archipelago communities that has not too much production. The capacity of air blast freezing suitable for archipelago communities is on the household scale. When designing and creating a home-scale air blast freezer is required caution, since failure in design will result in uneven product freezing[10]. Studies related to the design of today's air blast freezing focus on the cooling air distribution characteristics. Study of cold air distribution characteristics performed by Justo et al.[11], stating that using a Computational Fluid Dynamic (CFD) simulation can improve cooling room design for better cold air distribution optimize fan power so as to reduce total energy consumption by 12%. A special study of the characteristic design of cooling air distribution in the freezing process of fish products with industrial air blast freezing has been carried out by Walnuma et al. [12], using Modelica simulations suggests that in general this model can be a useful tool for visualization of austerity measures energy. However, studies on simulation models of air blast freezing refrigeration systems on a household scale are still difficult to find. system, so it is proposed to use a two-stage cascade refrigerating system to overcome this [13]. I n t he t wo-stage cas cade r efrigeration s ystem, t he choice of r efrigerant pai rs i n high- temperature circuits (HTC) and low-temperature circuits (LTC) determines the performance of the r efrigeration s ystem, but kas i s tudy only in s imulation m odels, t here is no val idation and evaluation with experimental data[14]. The study of the two-stage cascade refrigeration system simulation model design and validation of the model with testing is still rarely encountered.

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Characteristics Study of Two-Stage Cascade Refrigeration System Design for Household Air Blast Freezing

Based on what has been described above, the research proposed will concentrate on the design of the two-stage cascade refrigeration system, validate and evaluate the model with the experimental data. The main target of this research is to find for design parameters and operation of hous ehold ai r bl ast f reezing i n order t o i mprove t he e conomic r esilience of archipelago communities. 2. METHOD This r esearch i s pr eceded by des ign for r efrigeration s ystem f ollowed by t esting to obtain operational par ameters which f urther val idation and anal ysis of the des ign and operational parameters of t his ai r bl ast f reezer r efrigeration s ystem. T he des ign of t he t wo-stage cascade refrigeration system aims to obtain the appropriate temperature and pressure. The initial design of the cooling system aims to obtain the appropriate temperature and pressure. This simulation uses the R EFPROP 8 software[15] to determine the thermodynamic property that is needed and by looking at some of the state points shown in Fig. 1.

Figure.1. P-h diagram and a simple scheme of a two-stage cascade refrigeration system Balance equations are applied to find the mass flow rate of each cycle, the work input to the compressor, the heat transfer rates of the condenser and the cascade heat exchanger. The equation used in the analysis is as follows. Mass balance ∑m& =∑m& in out (1) Energy balance Q& − W& = ∑m& .h − ∑m& .h out in (2) Specific equations for each system’s components are summarized in table 1.

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Table.1. Balance equations for each system component Component mass energy High-temperature circuit m& = m& W& = m& h − h Compressor 6 5 H 5 ( 6s 5 ) & m& = m& Q = m& (h − h ) Condenser 7 6 C 7 7 6 Expansion device m& = m& h = h 8 7 8 7 & Cascade condenser m& = m& , m& = m& Q = m& (h − h ) = m& (h − h ) 5 8 3 2 cas 5 5 8 3 3 2 High-temperature circuit & & & & Compressor m2 = m1 W L = m1 (h2 s − h1 ) Expansion device m& = m& h = h 4 3 4 3 & evaporator m& = m& = & − 1 4 QE m1 (h1 h4 ) The system’s Coefficient of Performance (COP) has been calculated by the following equation: & Q COP = E W& +W& H L (3) Furthermore, the results of the analysis of temperature, pressure and refrigeration capacity obtained were used as input data to calculate the diameter and length of capillary pipes using DanCap software[16]. The cascade refrigeration cooling system test equipment consists of two refrigeration circuits, namely hi gh-temperature ci rcuit ( HTC) w hich w ill be f illed w ith R 22 r efrigerant and low- temperature circuit (LTC) which will be filled with R32 refrigerant. Testing is done by measuring the temperature out from compressors, condensers, expansion valves, cascade heat exchanger and evaporators, as well as pressure on high-pressure pipes and low-pressure pipes on before and after compressors on both HTC and LTC. Temperature measurements are carried out every 1 minute by the Arduino U no m icrocontroller w ith a digital D S18B20 waterproof thermometer sensor. Pressure measurement is carried out by analog pressure gauge. The voltage and current needed by the compressor are measured using digital clamp meter where the results of measurements of voltage and current are used to calculate the power absorbed by the compressor. The air velocity circulating in the cooling chamber is measured using a digital anemometer. Data retrieval is done up to a steady cooling system (steady state) which takes about 180 minutes. 3. RESULT AND DISCUSSION

3.1. DESIGN The difference between the ambient temperature and the target temperature of -40°C causes a high compression ratio and high energy requirements so that the compressor's performance is not stable. Therefore, the use of a two-stage cascade refrigeration system is expected to obtain a stable cooling system with small energy requirements. The reasons are using R22 and R32 refrigerants because the two refrigerants are easily found in the market. R22 and R32 each have a boiling point of -40.8°C and -53.15°C, so that R22 is used as a refrigerant on HTC and R32 for LTC. The assumptions taken when designing this two-level cascade refrigeration system include: 1. HTC condensers are cooled by air using the temperature of the average outside air in Indonesia based on SNI standards, namely 34°C dry bulb and 28°C wet bulb so that 40°C temperature condenser and 35°C subcooling are taken.

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Characteristics Study of Two-Stage Cascade Refrigeration System Design for Household Air Blast Freezing

2. Evaporating temperature HTC 0°C and superheating 15°C 3. Temperature difference in the 5°C cascade heat exchanger 4. Evaporating temperature LTC -40°C and superheating -5°C. 5. Cooling capacity is 0.5 kW. 6. Adiabatic compression with isentropic 0.75 efficiency both in compressors on HTC and LTC. 7. Negligible pressure and heat losses/gains in the pipe networks or system components. 8. Isenthalpic expansion across expansion valves. 9. Negligible changes in kinetic and potential energy All t hermo ph ysical p roperty r efrigerants ar e ob tained f rom R EFPROP 8 s oftware [15]. Thermodynamic state points of the cascade refrigeration system are presented in table 2.

Table.2. Calculation of thermodynamic state points of cascade system using REFPROP 8 Evaporator outlet Compressor outlet Condenser outlet Exspansion device outlet High-temperature circuit

P 5 = f (Tcas,E, x=1) P 6=P7 P7=f (TC, x=0) P8=P5

T5= Tcas,E T6=f (P6, S5) T7=T C T8= T cas,E

h5 = f (T5, P5) h6s = f (P6, S5) h7= f (T7, P7) h8=h7

S5 = f (T5, P5) h6 = (h6s – h5)/ηisent+ h5 S7= f (T7, P7) S8= f (P5, h8) Low-temperature circuit

P1 = f (TE , x=1) P2=P3 P3=f (Tcas,C, x=0) P4=P4

T1 = TE T2=f (P6, S1) T3= T5 – DT=Tcas,C T4 = TE

h1 = f (T1, P1) h2s = f (P2, S1) h3= f (T3, P3) h4=h3

S1 = f (T1, P1) h2 = (h2s – h1)/ηisent + h1 S3= f (T3, P3) S4= f (P1, h4) The REFPROP 8 software is used to determine the thermodynamic property and get the state points as shown in Fig. 2.

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Figure.2. P-h diagram design state points of the two-stage cascade refrigeration cycle

Table.3. the results of calculating the two-stage cascade refrigeration system design

 (kW)  (kW)   (kW)  (kg/s) High-temperature circuit 0.691 0.161 0.853 0.003996966 High-temperature circuit 0.5 0.191 0.691 0.00154335 Furthermore, based on The results of calculating the two-stage cascade refrigeration system design m odel i n T able 3, D anCap s oftware i s us ed t o obt ain t he l ength and di ameter of the capillary pipe which functions as an expansion tool both in high temperature circuits and low temperature circuits.

3.2. EXPERIMENT Experiment results of the cas cade refrigeration s ystem performance and comparison of its performance with the measured design are based on the coefficient of performance ( COP) as shown in Fig. 3. It can be seen that the COP value of the test result is 1.018, it is lower than the design which is 1.418, this is because the experiment refrigeration capacity more small than the estimated refrigeration capacity in the refrigeration system design.

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Characteristics Study of Two-Stage Cascade Refrigeration System Design for Household Air Blast Freezing

Figure.3. Performance comparisons of design and experiments The refrigeration capacity of experiment smaller than design because the refrigeration cycle of the R32 refrigerant in LTC does not reach the sub cooling phase when entering the expansion valve. This can be seen from the actual LTC refrigeration cascade cycle in the ph diagram as shown in Fig. 4. No achievement of sub cooling phase in condensing LTC is not because HTC are unable to cool condenser LTC but rather due to ineffective exchange process heat in a cascade heat exchanger. The effectiveness of the cascade heat exchanger is only 0.63, which means that only 63% of the heat at HTC can be absorbed by LTC, as shown in Fig. 5.

Figure.4. P-h diagram experiment state points of the two-stage cascade refrigeration cycle The value of the effectiveness of the heat exchanger is influenced by the temperature in and out of the f luid i n the heat exchanger . F ig. 5 shows a comparison of t he i nlet and outlet temperature of the cascade heat exchanger as time increases. To get a high effectiveness value, the hot fluid exit temperature must be close to the cooling fluid inlet temperature. In Fig. 5, it can be seen that there is a temperature difference of ±7°C between the exit temperature of R32 (T3)

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Darwin R.B Syaka, I Wayan Sugita and Muhammad Bijaksana refrigerant and the temperature entry of refrigerant R22 (T8) in the cascade heat exchanger; this indicates that the heat exchanger used is less able to exchanger heat effectively.

Figure.5. Cascade heat exchanger temperatures In Fig. 6 shows a comparison of the temperature of the evaporator and the temperature of the cooling room along with increasing time. A very significant decrease in temperature at the initial 60 minutes after ignition and in the last 60 minutes the test temperature starts to stabilize. In Fig. 5, i t can be s een t hat t here i s a di fference i n t emperature ±10°C bet ween t he evapor ator and cooling room, this indicates that the evaporator used is less able to absorb heat from the cabin effectively. However, the target coolant temperature around -30°C has been reached

Figure.6. Temperatures of evaporator and cooling room Measurement the airflow velocity occurring in the evaporator is only 2.65 m/s. this means still below the required airflow velocity for air blast freezing of at around 4 m/s [10]. This is what makes the temperature difference between evaporator and air-cooling room still quite large

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Characteristics Study of Two-Stage Cascade Refrigeration System Design for Household Air Blast Freezing 4. CONCLUSIONS According to the results of this research, some conclusions can be drawn as follows: • The design of the two-stage cascade refrigeration system R22 / R32 can be supported by using Refprop 8 and DanCap software. • The experiment results obtained are obtained the COP value 1.018 at the temperature evaporator -40 ° C. • Based on the analysis of the performance evaluation of the actual two-stage cascade refrigeration s ystem i s l ower t han t he des ign due t o t he i neffective heat exchange process in the cascade heat exchanger. ACKNOWLEDGMENTS This research was support by Hibah Penelitian Dasar U nggulan Perguruan Tinggi Tahun Anggaran 2018, Director General of Higher Education, Minister of Research, Technology and Higher Education. NOMENCLATURE COP [-] Coefficient of performance DT [oC] Temperature difference in the cascade-condenser h [kJ/kg] Specific enthalpy

hs [kJ/kg] Specific enthalpy calculated at suction entropy m& [kg/s] Mass flow rate P [bar] Pressure Q& [kW] Heat transfer rate S [kJ/kg.K] Specific entropy T [oC] Temperature W& [kW] Work x [-] Quality Special characters η [-] Efficiency Subscripts cas Cascade E Evaporator C Condenser H High-Temperature circuit isent Isentropic L Low-Temperature circuit s Isentropic

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[3] E. Muela, C. Sañudo, M. M. Campo, I. Medel, and J. A. Beltrán, “Effect of freezing method and frozen storage duration on lamb sensory quality,” Meat Sci., vol. 90, no. 1, pp. 209–215, 2012. [4] A. Tanaka, “A Novel Method a ‘Freeze-Blast’ Method Disrupt Microbial Cells to,” vol. 67, no. 1, pp. 52–56, 1989. [5] A. T . Y oshiyuki O mori, Ma sanori T sumura, T aizo I chida, H iroki N akajima, Mitsuyoshi Ueda, Fumihiko Sato, Yasuyuki Yamada, “Application of the Freeze-Blast Method to Disruption of Cultured Plant Cells,” J. Ferment. Bioeng., vol. 69, no. 2, pp. 132–134, 1990. [6] J. B. Dima, M. V. Santos, P. J. Baron, A. Califano, and N. E. Zaritzky, “Experimental study and numerical modeling of the freezing process of marine products,” Food Bioprod. Process. vol. 92, no. 1, pp. 54–66, 2014. [7] L. A. Espinoza Rodezno et al., “Cryogenic and air blast freezing techniques and their effect on the quality of catfish fillets,” LWT - Food Sci. Technol., 2013. [8] J. M. Chourot, H. Macchi, L. Fournaison, and J. Guilpart, “Technical and economic model for the freezing cost comparison of immersion, cryomechanical and air blast freezing processes,” Energy Convers. Manag., vol. 44, no. 4, pp. 559–571, 2003. [9] R. J. Dossat, Principles of Refrigeration, 4th ed. London: Pearson Education, 1997.

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