Case Study: Designing Air-to-Air Heat Exchanger With Heat Pipes

Advanced Thermal Solutions, Inc. (ATS) engineers were tasked by a client to design an air-to-air, aluminum heat exchanger with multiple copper heat pipes that could meet high power demands (more than 400W) with a thermal resistance requirement of 0.046°C/W and could withstand a wide range of ambient temperatures from -40°C to 60°C. Also, the separation between the heat pipe’s evaporator and condenser sections needed to be air tight.

Heat Exchanger

ATS engineers were tasked with designing an air-to-air heat exchanger with heat pipes that would fit inside an enclosure. (Advanced Thermal Solutions, Inc.)

Using analytical modeling, ATS engineers calculated the system pressure drop from the heat pipe to the fin block to the flow turn and also the thermal performance of the fins in ducted flow to determine the proper amount of fins to avoid over pressurizing the fans, while at the same time meeting the thermal resistance demands of the system. It was calculated that a maximum of 14 fins per inch could be used, while the overall size was well within the client’s requirements.

Challenge: To design an air-to-air heat exchanger that could handle high power demands of more than 400W and specific requirements on thermal resistance (0.046°C/W).

Chips/Components: Electronics junction box that requires internal air cooling.

Analysis: ATS engineers conducted analysis of the pressure drop across the system from the heat pipe to the fin block to the flow turn section, as well as analyzing the thermal performance of the entire heat exchanger. This analysis included calculating the ducted flow, heat transfer coefficient, and the fin and heat pipe resistance of the exchanger. The analysis also explored the difference between designs with copper and with aluminum fins.

Design Data: The data showed that thermal resistance and pressure drop of the CFD model were within 16% of the analytical model. The thermal performance of the heat exchanger with heat pipes was 0.044°C/W, meeting the client’s requirements.

Solution: The ATS design was optimized for four heat pipes and a suggestion was made to enhance the heat exchanger by using copper fins, rather than aluminum, because of a higher fin efficiency and lower thermal resistance.

Net Result: The customer was supplied with a production design of a heat exchanger block with heat pipes that could fit into the enclosure and provide the necessary forced convection cooling to maintain the proper temperature for the system. ATS also supplied the heat exchangers from the prototype stage to production.

For more information about Advanced Thermal Solutions, Inc. thermal management consulting and design services, visit www.qats.com or contact ATS at 781.769.2800 or ats-hq@qats.com.

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