Experimental and numerical study of a falling film absorber in an ammonia-water absorption chiller

Abstract

In this paper,experimental and numerical studies of heat and mass transfer in a falling film absorber are presented. The investigated absorber is a plate heat exchanger used ina falling film configuration. The ammonia-water solution flows in a falling film mode along the plates. The vapour flows co-current with the falling film and the coolant fluid is in a countercurrent flow with the falling film. A prototype of ammonia-water absorption chiller isused to experimentally study the absorber behaviour in real operating conditions. Amacro study of the absorber and a local analysis deduced from local temperatures measurements along the falling film are presented. A numerical model and a simulation tool aredeveloped in order to complete the experimental investigations.The associatednumerical parametric studyaims to separatethe coolant mass flow rate impact.The model is validated with experimental dataand a maximal relative error of 15 % is observedbetween experimental and numerical results. The results of this study suggest that during the absorption process,mass transfers are controlled by the falling film mass transfer resistance and that the liquid-side heat transfer resistance is negligible.

Variations of thermophysical properties and heat transfer performance of nanoparticle-enhanced ionic liquids

“…In an absorption refrigerator, the absorber takes in the refrigerant from the evaporator and thereafter releases it to the condenser in the desorber accompanied by exothermic and endothermic effects. At present, the commonly used working pairs in absorption refrigeration cycles are aqueous solutions of lithium bromide (H 2 O/LiBr) [3] and ammonia (NH 3 /H 2 O) [4]. Unfortunately, their broader industrial application has been hindered by the inherent defects of crystallization, corrosion, high working pressure and toxicity [5].…”

A critical review of heat and mass transfer correlations for LiBr-H 2 O and NH 3 -H 2 O absorption refrigeration machines using falling liquid film technology

“…Goel and Goswami [72,73], and Triché et al [74] used the Wilke correlation [43] to compute the heat transfer coefficient for the laminar flow regime, in which Wilke [43] studied the falling film heat transfer, and Kandlikar [75]…”

Experimental investigation of heat and mass transfer in a LiBr-H2O solution falling film absorber on horizontal tubes: Comprehensive effects of tube types and surfactants

“…Zhao et al [3] discussed the subcooled falling film heat transfer on a horizontal tube, and analyzed the effects of film flow rate, heat flux, inlet liquid temperature, tube diameter and liquid distributor height. Triché et al [4] analyzed the absorption process in a falling film absorber by experimental and numerical methods, and the results showed that mass transfers are controlled by the falling film mass transfer resistance. Álvarez and Bourouis [5] investigated the heat and mass transfer performance in a horizontal tube falling film absorber, and the working pair were aqueous (lithium, potassium, sodium) nitrate solution.…”