Design, Fabrication, and Testing of Cross Flow Micro Heat Exchangers.

Abstract

Cross flow micro heat exchangers were designed to maximize heat transfer from a liquid (water) to a gas (air) for a given frontal area while holding the pressure drop across the heat exchanger of each fluid to values characteristic of conventional scale heat exchangers (car radiators). The cross flow micro heat exchanger design is unique since it produces a very high rate of heat transfer/volume between dissimilar fluids with low fluid pressure drops. Predicted performance for two types of cross flow micro heat exchangers is compared to each other and to current innovative car radiators. Although the cross flow micro heat exchanger has a lower rate of heat transfer/frontal area, it can transfer more heat/volume or mass than existing heat exchangers within the context of the design constraints specified. This can be important in a wide range of applications (automotive, home heating, and aerospace). One type of cross flow micro heat exchanger was fabricated by aligning, then bonding together, two plastic parts that had been molded using the LIGA process. The other type of heat exchanger was fabricated by first electroless plating a layer of nickel over a plastic part molded using the LIGA process, then dissolving the plastic. Performance of the fabricated heat exchangers was measured and compared to the predicted performance. At the design constraints, the mathematical model predicted the fluid pressure drops and heat transfer performance within 10% of the measured performance for the fabricated cross flow micro heat exchangers.