High Performance Micro-Grooved Evaporative Heat Transfer Surface for Low Grade Waste Heat Recovery Applications

Abstract

The continued demand for high performance electronic products and the simultaneous trend of miniaturization has raised the dissipated power and power densities to new unprecedented levels in electronic systems. Thermal management is becoming increasingly critical to the electronics industry to satisfy the increasing market demand for faster, smaller, lighter and more cost effective products. Utilization of waste heat for the purpose of cooling chip is a promising area for enhancing the thermal management and net energy efficiency of the system. This paper focuses on the development of a tubular microgrooved evaporator and its performance characterization based on heat transfer coefficients and pressure drop measurements. Channel with aspect ratio of 3:1 (channel width – 100 μm, channel height – 300 μm) microgrooved structure was used in the evaporator. The system has been tested with R134a as refrigerant for refrigerant flow rate range of 0.005–0.02 kg/s and water flow rate range of 0.25–0.65 kg/s. Very promising results has been obtained in preliminary investigation. Heat transfer coefficient as high as 13,500 W/m2k has been obtained which is almost five times higher than comparative state of art technologies. The associated pressure drop is quite modest and much less than state of the art conventional evaporators.

Next Generation Microchannel Heat Exchangers

“…More recently, micro-structured surface (Campbell et al 2006) 82 3 Emerging Applications of Microchannels evaporators and condensers were repackaged to a tubular configuration to simplify fabrication and increase operation pressure. The first published information about tubular configuration is presented in (Jha et al 2011).…”

“…The outer side is used for refrigerant (R134a) Fig. 3.23 a Schematic of the force-fed evaporation process; b tubular evaporator (Jha et al 2011) flow, where medium aspect ratio microgrooves with hydraulic diameter of 150 lm and inner side minigrooves with hydraulic diameter of 600 lm were used. The HX tube was fabricated at Wolverine MicroCool Inc., utilizing patented microdeformation technology to attain medium to high aspect ratio channels.…”