Experimental development of the plate shower heat exchanger to reduce the domestic hot water energy demand

Abstract

The article describes an experimental development of a new prototype of the horizontal plate shower exchanger for wastewater heat recovery. The prototype is designed so that while achieving the highest possible value of efficiency, it also respects the requirements of the spatial arrangement of the heat exchanger casing and, thus, allows an appropriate flow of wastewater on both sides of the heat transfer surface. At the same time, emphasis is placed on the smallest possible height of the heat exchanger casing with regard to the minimisation of the built-up space and the expected wastewater flow during the shower cycle. Experimental testing was performed according to the conditions meeting the certification criteria of the Passive House Institute, while for a given heat exchanger, the investigated flows and water temperatures, as well as the heat transfer efficiency of the new prototype was determined, reaching peak values ​​of up to 62%. An energy analysis and derivation of the equation was also performed, according to which it is possible to determine the achieved heat savings in the preparation of domestic hot water from the heat transfer efficiency of the exchanger, including all heat losses of the system. With new prototype, heat savings more than 21% are achieved.