Choon-Geun Moon

A study on the advanced performance of an absorption heater/chiller with a solution preheater using waste gas

Abstract A large amount of consumed energy is released to the environment as waste heat, which may be used directly in some applications for useful purposes. Thus, from the standpoint of energy conservation, it will be meaningful to investigate systems with waste heat utilization. It has long been indicated that absorption cycles may have good potential applications for enhancing energy conservation via waste heat recovery. As such they have often been identified as an appropriate subject for research and development. Along this line, this paper also examines the development of an absorption cycle with waste heat utilization. More specifically, this study investigates a double-effect LiBr–water absorption cycle which uses exhaust gases from the burner of the high-temperature generator to preheat the weak absorbent solution on its way from the absorber to the low-temperature generator. The overall performance of the absorption heater/chiller system is analyzed and discussed on the basis of experimental results.

Experimental study of heat and mass transfer on an absorber with several enhancement tubes

An experimental study of the absorption process of water vapor into a lithium bromide solution was performed. For the purpose of the development of a high-performance absorption chiller/heater utilizing a lithium bromide solution as the working fluid, it is the most effective way to improve the performance of the absorber with the largest heat transfer area of the four heat exchangers. This paper considers a bare tube, bumping bare tube, floral tube, and twisted floral tube for the absorber of an absorption chiller/heater. The floral and twisted floral tubes have about 40% higher heat and mass transfer performance than the bare tube conventionally used in an absorber. Therefore, floral and twisted floral tubes are expected to realize high heat and mass transfer performance.

Performance Characteristics of a Closed-Circuit Cooling Tower With Multiple Paths

The performance of a closed-circuit wet cooling tower (CWCT) with multiple paths having a rated capacity of 9 kW has been studied experimentally. When the CWCT has to operate with a partial load, the required quantity of cooling water reduces and thereby the velocity of the process fluid inside the tubes decreases. The velocity of the process fluid can be increased by installing blocking tubes in the heat exchanger. The test section in this experiment has multiple paths that have been used as the inlet for cooling water that flows from the top part of the heat exchanger. The heat exchanger consists of eight rows and 12 columns and the tubes are in a staggered arrangement. Heat and mass transfer coefficients and temperature drops were calculated with several variations including multiple paths. The results obtained from this study were compared with those reported and found to conform well. The investigation indicates that a CWCT operating with two paths has higher heat and mass transfer coefficients than with one path.

Heat Transfer Enhancement with Surfactants in Horizontal Bundle Tubes on Absorber

This research was concerned with the enhancement of heat transfer by surfactant added to the aqueous solution of LiBr. Different horizontal tubes were tested with and without an additive of normal octyl alcohol. The test tubes were a bare tube, floral tube and hydrophilic tube. The additive mass concentration was about 0.055.5%. The heat transfer coefficient was measured as a function of solution flow rate for the range of 0.010.034 kg/ms. The experimental results were compared with cases without surfactant. The enhancement of heat transfer by Marangoni convection effect generated by the addition of the surfactant is observed in each test tube. The increase of heat transfer coefficient by surfactant addition is about 3590% for bare tube, 4070% for the floral tube, 3050% for the hydrophilic tube and was higher for the cases with smaller a little solution flow rates.