Study of the condensation performance of composite coating on copper surfaces for use in solar-powered adsorption cooling systems

Abstract

An adsorption cooling system is a potential supplementary system for vapor compression systems because of its environmental friendliness and energy saving potential. Currently, there are still a number of technical challenges which limit the wide use of adsorption cooling systems, such as low efficiency, bulky size, high manufacturing cost, etc. In order to address these issues, a solar-powered adsorption cooling system and mathematic models have been developed to investigate the cooling performance of the adsorption cooling system. The effects of hot water inlet temperature, cooling water inlet temperature, hot water flow rate, adsorption/desorption phase time, mass recovery phase time, heat recovery phase time, pre-heating phase duration, solar collector area, and dead volume on the cooling performance were investigated. Moreover, a novel mass recovery was proposed and investigated. At a typical operating condition, a SCP of 208.2 W/kg, a COP of 0.24, and an EER of 4.5 were achieved. In addition, the experimental results had a good agreement with the simulation results. Various surface coatings (i.e. superhydrophilic surface, superhydrophobic surface, superhydrophilic/adsorbent composite surface, and superhydrophobic/adsorbent composite surface) were designed and investigated to improve the performance of the condenser. In order to study the enhancement of the heat transfer coefficient and condensation rate, an experimental set up was developed to test the condensation rate. The effects of cooling water inlet temperature, relative humidity, various surfaces, and patterns of the composite surfaces on the contact angle and condensation rate were investigated. A condensation rate of 49.3 g/m²min on the superhydrophobic/adsorbent composite surface was achieved, showing an improvement of 49.9 % compared with that of a copper surface under the operating condition with a cooling water inlet temperature of 7 °C and a relative humidity of 95 %. Moreover, the cooling performance of the adsorption cooling system utilizing the composite surface in the condenser was numerically investigated. A SCP of 231.4 W/kg and a COP of 0.317 were estimated, which showed an improvement of 25.0 % and 7.8 %, respectively, compared with that of the system without coating the composite surface.

Date of Award	2018
Original language	English
Awarding Institution	The Hong Kong University of Science and Technology