Experimental analysis of a H2O-LiBr vapour absorption cooler based on bubble pump technique and hydrostatic principle are presented. Heat input to the bubble pump and boiler, pump lift/driving head and weak solution concentration are varied to analyze the system performance. The cooler is tested at different load conditions, i.e., at no load, pull down load and steady load conditions. Results indicate that coefficient of performance of about 0.50 could be attained for the boiler temperature of 85 °C and condenser and absorber temperatures in excess of 40 °C. © 2003 Elsevier Ltd. All rights reserved.

M. Prakash Maiya

Department of Mechanical Engineering

Absorption

Coolants

Refrigerators

BUBBLE PUMPS

Pumps

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Experimental analysis of a bubble pump operated H2O–LiBr vapour absorption cooler

Applied Thermal Engineering

Miniaturization of the absorption refrigerator requires an air cooled absorber and condenser and replacement of the customary solution pump by a bubble pump. The operating pressures in the bubble pump operated two fluid vapour absorption refrigerator have to be very low (vacuum) so as to make use of the hydrostatic principle to maintain the required pressure difference between the condenser and evaporator. Hence, only water and alcohol based working fluid combinations are found suitable. Thermodynamic properties, such as specific heat and heat of mixing, and thermophysical properties, such as vapour pressure, density, viscosity, surface tension and solubility, are necessary for the overall performance evaluation of such a refrigerator. In this paper, sixteen water based working combinations have been analyzed and compared with reference to the solution density governing the hydrostatic height, viscosity and specific heat affecting the heat and mass transfer and solubility to avoid crystallization.

Energy Conversion and Management

Influence of thermodynamic and thermophysical properties of water-based working fluids for bubble pump operated vapour absorption refrigerator

The hydrostatic principle and bubble pump technique are used in the two-fluid pumpless continuous vapour absorption refrigerator to create the circulations of the solution and refrigerant. In this paper, the bubble pump, which is the 'heart' of this natural circulation type of refrigerator, has been investigated both analytically and experimentally. The bubble pump is modelled for intermittent slug flow of solution and vapour mixture. A test rig is built in glass to evaluate the performance of the bubble pump, to visualize the flow behavior and to validate the analytical model. Bubble pump tube diameter, pump lift, driving head and heat input are varied to analyze the pump performance. Results indicate that pumping ratio is nearly independent of the heat input, but increases with decrease in pump tube diameter, decrease in pump lift and increase in driving head. © 1998 Elsevier Science Ltd and IIR. All rights reserved.

International Journal of Refrigeration

Studies on bubble pump for a water-lithium bromide vapour absorption refrigerator

Miniaturization of an alcohol-based absorption refrigerator requires an air-cooled absorber and condenser and the replacement of customary solution pumps by the bubble pump. Evaluation of such a refrigerator requires thermodynamic (specific heat and heat of mixing) and thermophysical (vapour pressure, density, viscosity, surface tension and solubility) properties of refrigerant-absorbent solution. These property correlations for five alcohol-based working combinations, majority of them obtained by curve fitting, have been complied and presented in this paper along with their validity ranges and percentage of error. The working fluids have been analyzed and compared with reference to the solution density governing the hydrostatic height, viscosity and specific heat affecting the heat and mass transfer and solubility to avoid crystallization. Further the variations of performance parameters like cut-off temperature, circulation ratio, coefficient of performance and efficiency ratio of these working fluids with respect to various operating conditions are discussed.

International Journal of Energy Research

Comparison of methanol-based working fluid combinations for a bubble pump-operated vapour absorption refrigerator

Miniaturisation of the vapour absorption refrigerator requires replacement of the solution pump by a heat operated bubble pump and air cooled condenser and absorber. The replacement necessitates the selection of working media restricted to vacuum operation, and the air cooling poses the problem of high pressure drops in the refrigerator. Thermodynamic analysis of the absorption refrigerator with such a suitable working medium is performed considering the pressure drops in the system as parameters. The analysis shows that the effect of the evaporator to absorber pressure drop on the system performance is more significant than that of the generator to condenser pressure drop, and it becomes more predominant at the low generator temperature normally encountered in solar operated systems. © 1997 Elsevier Science Ltd.

Journal	Applied Thermal Engineering
ISSN	13594311
Open Access	No