A passive evaporative cooling heat sink method for enhancing low-grade waste heat recovery capacity of thermoelectric generators

Abstract

In this study, we utilized a novel passive evaporative cooling heat sink (PECHS) to enhance the waste heat recovery capacity of a thermoelectric generator (TEG). When heat is applied to the PECHS placed across the TEG, convection heat dissipation and evaporative cooling occur on the fins, thus, greatly improving the TEG output capacity. We established a theoretical model of the PECHS cooled TEG, and investigated the effects of certain key parameters on the TEG output capacity. The results show that the TEG output capacity is positively correlated with the TEG hot side temperature (TH) and fin height (Lf), and inversely correlated with the ambient relative humidity (RH), ambient temperature (Tamb), and fin thickness (tf). However, as Lf increases, the rate of increase in the cooling capability of the PECHS decreases. Moreover, RH has a small impact on the TEG output capacity. Considering the heat dissipation capacity and cost, a PECHS needs to have an optimized number of fins (M). Consequently, the TEG open-circuit voltage (Uopen = 4.86 V) and maximum output power (Pmax = 4.1 W) were obtained under fixed conditions (TH = 150 °C, RH = 50%, Tamb = 20 °C, Lf = 35 mm, tf = 1 mm, M = 11). The results show that the Uopen and Pmax are 1.83 and 3.33 times of a normal heat sink case (Uopen = 2.66 V and Pmax = 1.23 W), respectively. The theoretical model was verified using the constructed experimental system. Our findings show that PECHS is an efficient passive cooling device and can potentially be used in cooling applications such as photovoltaic board cooling and building cooling.