Concept of integrating air conditioning system with thermoelectric units and double-pipe heat exchanger for efficient waste heat utilization: an experimental study.

In the vapor compression air conditioning system, a notable amount of heat dissipation is obvious. The condenser plays a critical role in maintaining the refrigerant phase prior to the expansion valve. Previous studies have primarily focused on recovering waste heat through conventional thermal routes. However, in automobiles and other allied fields, in addition to process heat, direct energy conversion techniques are also in practice. Hence, the present experimental study is an attempt to demonstrate the implementation of both electrical and thermal routes to extract waste heat to the maximum possible extent from the air conditioning system. For this exercise, Coolselector software was used to fetch the operating conditions, (including tonnages of 1.5 TR, 3.0 TR, and 4.5 TR) and later, the entire operations were simulated. The thermoelectric generator (TEG) array produced a decent level of electrical power with negligible drop in process fluid temperature. In the double pipe heat exchanger (DPHX), the secondary side could extract a good amount of heat. Hence to identify the best-case, exergy analysis was done separately for the TEG and the DPHX, in that the 3.0 TR case identified as the best. Further, to enhance system performance, inserts were used in the DPHX, resulting in 26% and 46% improvement in effectiveness for louvered tape and twisted tape configurations, respectively. Even condenser length optimization was carried out to understand the influence of various heat transfer augmentation techniques. Though this approach is still in the pre-mature stage, appropriate design of condensers, heat spreaders, and heat exchangers can yield remarkable results.