Experimental evaluation of a new mini square channel air-cooled heat exchanger for an absorption chiller

Abstract

• An air-cooled subcooler for absorption cooling systems is experimentally evaluated. • Square minichannels of 2 mm side and 11 cm length and natural or forced air are used. • Approach temperature, pressure drops and heat transfer parameters are obtained. • Correlations are derived for heat transfer and pressure drop in the subcooler. • A notable increase in the cooling power of the absorption system is obtained. A mini square channel air-cooled heat exchanger, operating as subcooler in the typical temperature range of absorption cooling systems, is experimentally evaluated. Working fluid flows along 82 square minichannels of 2 mm side and 11 cm length, manufactured on stainless-steel. Hot fluid flows downward through the channels and two cases are evaluated: natural and forced air convection. In the last case, ambient air flows in the upward direction. Two additional operating parameters are modified: the inlet fluid temperature, between 34.8 and 75.4 °C and the fluid mass flow rate, in the range from 5.7 to 29.1 kg/h. Inlet and outlet temperature and pressure for the fluid and ambient temperature are measured, while the air velocity is kept constant at 0.75 m/s. Results obtained for the approach temperature, pressure drops, heat transferred and heat transfer coefficients for the air-cooled subcooler are provided. Correlations are derived to predict the heat transfer coefficient and pressure drop of the subcooler. Integration of the air-cooled subcooler in a single-effect absorption cooling system is evaluated, showing a notable increase in the cooling power mainly in the case of using forced air flow.