Experimental characterization of a nickel alloy-based manifold-microgroove evaporator

Effective heat and mass exchangers are vital for further improvement of absorption cooling systems. In the current study, a novel manifold-microchannel evaporator was developed and tested. This paper reports heat transfer coefficients and pressure drop for a nickel alloy-based tubular microgrooved evaporator consisting of a novel manifold guided flow. The evaporator was designed for refrigerant-to-liquid heat exchange, and the heat transfer surface consisted of fine high-aspect-ratio microchannels having 100 m channel width and 600 m channel height. The refrigerant-side flow was guided through square manifold feeds with sides of 2 mm in length. A tube insert providing an annular gap of 2.5 mm was used on the water side. Experiments were conducted with R134a as the refrigerant for a flow rate range of 5-30 g/s and water-side flow rate range of 100-600 ml/s. An overall heat transfer coefficient of more than 10,000 W/m²-K was measured with a modest maximum pressure drop of 120 mbars and 100 mbars on the refrigerant and water sides, respectively.