The new concept of capillary forces aided evaporator for application in domestic organic rankine cycle
This paper presents studies on the possibility of applying capillary forces induced in the porous structure to a modern design of evaporator. The potential application of such heat exchanger is for example an evaporator of the domestic micro combined heat and power (CHP) unit. One of the problems in the micro-CHP is excessive demand for pumping power. The proposed design helps in overcoming that issue. In the evaporator outlined in thepaper, there is a possibility of reducing the demand for pumping power, as the evaporator produces the extra pressure effect due to action of capillary forces. If successful, the cycle circulation pump operates only to compensate the pressure drop due to friction losses in the loop, whereas the wick covers the demand to overcome the pressure drop in the expansion device. Out of 14 tested fluids 3 were selected for further scrutiny, namely ethanol, water, andammonia. It has been assumed that the fluid should work in the evaporator at temperature of 160°C. The results of surface tension distributions with respect to temperature are been presented in the figures. Preliminary analysis of the results indicates that water has the best potential; however, taking all issues into account, it can be said that the best effect is obtained using ethanol.
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