International Journal of Metallurgical & Materials Science and Engineering (IJMMSE) ISSN 2278-2516 Vol. 2 Issue 4 Dec - 2012 1-10 Š TJPRC Pvt. Ltd.,
CONFIGURATION OF A 2 Kw CAPACITY ABSORPTION REFRIGERATION SYSTEM DRIVEN BY LOW GRADE ENERGY SOURCE 1 1
ANIL SHARMA, 2BIMAL KUMAR MISHRA, 3ABHINAV DINESH & 4ASHOK MISRA
Department of Production Engineering, Birla Institute of Technology- Extension Centre, Deoghar, India 2
3
Department of Applied Mathematics Birla Institute of Technology- Mesra, Ranchi, India
Department of Electronics & Communication Engineering, Birla Institute of Technology- Extension Centre, Jaipur, India 4
Department of Mechanical Engineering, Birla Institute of Technology- Mesra, Ranchi, India
ABSTRACT Consistently increasing CO2 emission and ozone depletion from CFC’s are serious environmental issues challenging scientific community. The dependence on fossil fuels has to be reduced and alternative environmental friendly options need to be explored. In this aspect, vapor absorption system gives scope of utilizing low grade energy source i.e. solar panel for generating cooling effect which is dominated by high grade energy driven compression technology. The LiBr aqueous solution based absorption cycle consists of four stages: generation, condensation, evaporation and absorption with ideally no moving part. In this paper, a configuration of 2kW capacity LiBr-Water based absorption refrigeration system is presented. The selection of evaporator capacity i.e. 2kW guides the operating conditions of other component in the cycle. Empirical correlations had been used to determine heat transfer rate. Based on these results specification for heat exchangers are established. This configuration serves as a platform to design for manufacturing of such systems.
KEY WORDS: Absorption Cycle, Low Grade Energy, Overall Heat Transfer Coefficient, System Configuration INTRODUCTION In a basic absorption cycle, low pressure refrigerant vapor is converted to a liquid phase (solution) at same pressure. This conversion is made possible by the vapor being absorbed by a secondary fluid called absorbent. Absorbent absorbs refrigerant because of the mixing tendency of miscible substances, and an affinity between absorbent and refrigerant molecules. Thermal energy is released during this absorption process and should be transferred to a sink. Among various absorbent and refrigerant pair, LiBr- Water is most promising in chiller application due to high safety, high volatility ratio, high affinity, high stability and high latent heat. The working temperature for this pair should be above 00C, because the refrigerant turns to ice at this temperature. The properties of this pair are vastly documented in literature, in this paper, the properties of LiBr aqueous solutions are referred from the reference [3]. In the cycle shown in figure 1, water vapor evaporate and separates from aqueous LiBr solution in generator, and increases the concentration of LiBr in solution. For this process heat is supplied from external source. At the same pressure, the water vapors from generator are condensed in condenser and this condensed water is throttled to the evaporator at low pressure. Due to reduced pressure, the water change phase and evaporate by taking latent heat of vaporization in the evaporator at chiller temperature and generates the cooling effect. At same pressure, the vapors from evaporator are absorbed by LiBr-aqueous solution supplied form generator having higher concentration of LiBr. The absorption of water vapor reduces the concentration of LiBr in aqueous solution, this solution is then passed to generator