UNIT 1: Safety in Workshop & Introduction of Air Conditioning System

UNIT 2: Introduction of Air conditioning System.

1. OBJECTIVES The objectives of this unit are following: a. Understand the function of Air conditioning and freezer system. b. Understand the type of Air conditioning system. c. Understand the basic components of Air conditioning system

2. EQUIPMENTS 2.1 AIR CONDITIONING EQUIPMENT a. Chiller unit b. Split unit. c. Refrigerator.

3. WORKSHOP a. Power generation lab b. Environment lab.

4. INTRODUCTION OF AIR CONDITIONING

An air conditioner is an appliance, system, or mechanism designed to stabilize the air temperature and humidity within an area (used for cooling as well as heating depending on the air properties at a given time), typically using a refrigeration cycle but sometimes using evaporation, most commonly for comfort cooling in buildings and motor-cars. The refrigeration process can best be described as the transfer of heat from one place to another. The process of air conditioning, therefore, involves removing heat from inside a structure or residence and depositing the heat outside. There are various types of air conditioning systems; the application of a particular type of system depends upon a number of factors like area to be cooled, the total heat generated inside the enclosed area. Here the various types of air conditioning systems.  Window air conditioner  Split and Packaged air conditioner.  Central air conditioning system.  Central water chiller.

Unit 2 –Introduction of air conditioning Mechanical Engineering Practice III (BDA 2801) Faculty of Mechanical and Manufacturing Engineering 2-2

 Automobile Air conditioning.

Window air conditioner: This is the most commonly used air conditioner for single rooms. In this air conditioner all the components, namely the compressor, condenser, expansion valve or coil, evaporator and cooling coil are enclosed in a single box. This unit is fitted in a slot made in the wall of the room. (See Figure 1).

Figure 1: Window air conditioner Split air conditioner The split unit is comprised of two parts: the outdoor unit and the indoor unit. The outdoor unit, fitted outside the room, houses components like the compressor, condenser and expansion valve. The indoor unit comprises the evaporator or cooling coil and the cooling fan. For this unit don’t have to make any slot in the wall of the room. The split air conditioner can be used to cool one or two rooms. (See figure 2).

Figure 2: Split air conditioner

Packaged air conditioner Packaged air conditioner is used for cool more than two rooms or a larger space at home or office. There are two possible arrangements with the package unit. In the first one all the components, namely the compressor, condenser (which can be air cooled or water cooled), expansion valve and evaporator are housed in a single box. The cooled air is thrown by the high capacity blower, and it flows through the ducts laid through various rooms. In the second arrangement, the compressor and condenser are housed in one casing. The compressed gas passes through individual units, comprised of the expansion valve and cooling coil, located in various rooms. (See Figure 3).

Figure 3: Packaged air conditioner

Central air conditioning system The central air conditioning system is used for cooling big buildings, houses, offices, entire hotels, gym, cinema hall, factory etc. If the whole building is to be air conditioned, HVAC engineers find that putting individual units in each of the rooms is very expensive initially as well in the long run. The central air conditioning system is comprised of a huge compressor that has the capacity to produce hundreds of tons of air conditioning. Cooling big halls, malls, huge spaces, galleries etc is usually feasible with central conditioning units only. (See Figure 4).

Figure 4 : Central air conditioning system

Central water chiller.

Large central water chiller that supplies a large quantity of chilled water between 40°F and 46°F to air conditioning units in a building (Show in figure 5). In concept, the water chiller is no more complex than the simple drinking fountain. In sizes over 100 tons, the compressors are centrifugal or screw-type instead of reciprocating (Figure 6). Many of the larger units use R- 11, Which is a low pressure, high volume refrigerant. On these systems, the low-side pressure will be between 15 and 20 in. Hg (for saturated suction temperatures between 24°F and 42°F). The discharge pressures will be between 3 psi and 21 psi (at condensing temperatures between 65T and 125°F). A unique feature of systems that operate normally at a relatively deep vacuum is that any leakage on the low side of the system will result in air getting into the system rather than refrigerant leaking out. These systems are provided with purge systems that separate the air from the refrigerant, and operate periodically to expel this air.

Figure 5: Large (50 tons) reciprocating water chiller supplies 44°F water to the building air-handler units. (Courtesy The Trane Company)

Figure 6: Large (300 tons) centrifugal water-cooled water chiller. (Courtesy The Trane Company)

Automobile Air conditioning.

Air conditioning facilitates the removal of heat from inside the vehicle. The principle applied is that heat is removed by conduction and convection. An evaporator which is cold absorbs the heat from the air that is passed through it and then cold air is forced out through the vents inside the car by the blower motor. This is done by pressurizing refrigerant (134a) with a compressor and then releasing refrigerant (134a) inside the air conditioner evaporator.

Figure 7: Automotive air conditioner

Refrigerator / Freezer Refrigeration is the process of removing heat from an enclosed space, or from a substance, to lower its temperature. A refrigerator uses the evaporation of a liquid to absorb heat. The liquid, or refrigerant, used in a refrigerator evaporates at an extremely low temperature; creating freezing temperatures inside the refrigerator. Refrigerators from the late 1800s until 1929 used the toxic gases ammonia (NH3), methyl chloride (CH3Cl), and sulfur dioxide (SO2) as refrigerants. Several fatal accidents occurred in the 1920s when methyl chloride leaked out of refrigerators. Modern refrigerators usually use a refrigerant called HFC-134a (R134a), which has no ozone layer depleting properties. Refrigerators are extensively used to store foods which deteriorate at ambient temperatures. The fundamental reason for having a refrigerator is to keep food cold. Cold temperatures help food stay fresh longer. The basic idea behind refrigeration is to slow down the

Unit 2 –Introduction of air conditioning Mechanical Engineering Practice III (BDA 2801) Faculty of Mechanical and Manufacturing Engineering 2-7 activity of bacteria (which all food contains) so that it takes longer for the bacteria to spoil the food.

Figure 8: Refrigerator parts diagram The basic air conditioning system and refrigerator are made up of four major components that enable this heat transfer to take place. These components are (see figure 9): • Evaporator • Compressor • Condenser • Metering device / Thermal Expansion Valve

Figure 9: Basic refrigerant cycle

5. ACTIVITIES FOR AIR CONDITIONING

a. Identification of type air conditioning systems in working place, (Automotive Laboratory, Air-Conditioning Laboratory, power generation plant). b. Identify the major components of type air conditioning systems in working place. c. Identify the flow of air conditioning system for each type. d. Identify the part of refrigerator.

6. QUESTIONS

9.1. What is refrigerant process? 9.2. Explain the types of air conditioning system? 9.3. What is refrigerator? 9.4. Explain the major component of air conditioning system?

7. REPORT FOR AIR CONDITIONING

The student shall submit individual report that covers the entire item in the workshop activity using a study case given in the first week of this subject. Report content 10.1. Title 10.2. Objective 10.3. Introduction (20 %) 10.4. Work procedure. (30 %) 10.5. Observation.(20 %) 10.6. Conclusion (20 %) 10.7. Reference. (10 %)

Unit 2 –Introduction of air conditioning Mechanical Engineering Practice III (BDA 2801) Faculty of Mechanical and Manufacturing Engineering