Vapour Absorbtion Refrigeration free essay sample

The vapour absorption system uses heat energy, instead of mechanical energy as in vapour compression system, in order to change the condition of the refrigerant required for the operation of the refrigeration cycle. In this system, the compressor is replaced by an absorber, a pump, a generator, and a pressure reducing valve. This complete papers discuss about the theoretical calculations are made of different components of the systems like evaporator, absorber, condenser and pump of vapour absorption system for a capacity of 0. 5TR and experimentally developed and run system to validated for reducing the temperature for the free of cost of operation. Keywords: Absorption, absorber, NH3, VAR, VCR. I. INTRODUCTION In the vapour absorption refrigeration (VAR) system, a physicochemical process replaces the mechanical pro-cess of the vapour compression refrigeration (VCR) sys-tem by using energy in the form of heat rather than mechanical work. The main advantage of this system lies in the possibility of utilizing waste heat energy from industrial plants or other sources and solar energy as the energy input. The VAR systems have many favourable characteristics. Typically a much smaller electrical input is required to drive the solution pump, compared to the power requirements of the compressor in the VCR systems, also, fewer moving parts means lower noise levels, higher reliability, and improved durability in the VAR systems [1–5]. A Robur Servel ACD-3600 gas-? red system was originally obtained for a study of the suitability of VAR systems of road transport refrigeration. However, an early approach to the manufacturer for comprehensive details of the system characteristics received a negative response. It was therefore decided to conduct a detailed experimental analysis of the system. This work forms the basis of this paper. A vapour absorption refrigeration system is a heat operated unit which uses refrigerant (NH3) that is alternately absorbed by and liberated from the absorbent (water). The vapour absorption system uses heat energy, instead of mechanical energy as in vapour compression system, in order to change the condition of the refrigerant required for the operation of the refrigeration cycle. In this system, the compressor is replaced by an absorber, a pump, a generator, and a pressure reducing valve. These components in the system perform the same function as that of compressor in vapour compression system. The vapour refrigerant from evaporator is drawn into an absorber where it is absorbed by the weak solution of refrigerant forming a strong solution. This strong solution is pumped to the generator where it is heated by utilizing solar energy. During the heating process, the vapour refrigerant is driven off by the solution and enters into the condenser where it is liquefied. The liquid refrigerant then flows into the evaporator and thus the cycle is completed. The papers discuss about the complete theoretical calculations and design the system as per the theoretical calculations and experimentally validate the system with reducing the temperature. II. METHODOLOGY Fig. 1 shows the schematic diagram of a vapour absorption system. Ammonia vapour is produced in the generator at high pressure from the strong solution of NH3 by an external heating source. A solar cooker will produce the heat and generate ammonia gas. Ammonia gas then enters into the condenser. High pressure NH3 vapour is condensed in the condenser. The cooled NH3 solution is passed Vidyavardhini’s College of Engineering and Technology, Vasai Page 128 International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 National Conference on Emerging Trends in Engineering Technology (VNCET-30 Mar’12) through a throttle valve and the pressure and temperature of the refrigerant are reduced below the temperature to be maintained in the evaporator. The low temperature refrigerant enters the evaporator and absorbs the required heat from the evaporator and leaves the evaporator as saturated vapour. This caused the hot vapour from the generator to enter the evaporator coil without changing its phase completely and thus reduced the cooling effect. The system couldn’t sustain desired pressure range. The pressure capacity of the flexible hoses used in the system limited the system pressure and thus the design pressure could not be achieved due to fear of failure. Concentration of ammonia in the system design was for 50% concentration of ammonia but in the ammonia commercially available is of 25% concentration. This was also a limitation. IV. EXPERIMENTAL SETUP Based on above theoretical value calculations the all the components of system are assemble for the vapour absorption refrigeration system as shown in Fig. 2. 2 3 Fig. 2 Complete view refrigeration system. of vapour absorption REFERENCES [1] Dossat RJ. Principles of refrigeration. 2nd ed. New York: John Wiley and Sons; 1981. [2] Haseler LE, et al. A design study for absorption cycle heat pumps for domestic heating. Report no. G1157 UK: Engg. Sci. Div. , AERE Harwell; 1978a. [3] Haseler LE, et al. Absorption cycle heat pumps for domestic heating. Report no. G1049 UK: Engg. Sci. Div. ,AERE Harwell; 1978b. [4] Horuz I. An experimental study of the vapour absorption refrigeration in road transport vehicles. PhD thesis, Mech. Engg. Dept. , Univ. of Strathclyde, Glasgow, UK 1994. [5] Yamankaradeniz R, Horuz I, Coskun S. Refrigeration techniques and applications. Bursa Turkey: Vipas? A. S? ; 2002. V. RESULTS AND CALCULATION Fig. 3 Time–Temperature curve for vapour absorption refrigeration system. Vidyavardhini’s College of Engineering and Technology, Vasai Page 131