One underground heat exchanger for multiple heat pumps

A heat pump that is coupled thermally with the ground extracts heat from the soil in winter, and discharges heat in the summer. The coupling is made through a buried heat exchanger. In this paper we explore the idea of using a single heat exchanger that serves more than one heat pump. Each heat pump draws its mass flow rate from the heat exchanger and, in addition, a background flow rate circulates permanently through the heat exchanger. The places where the heat pumps are connected to the exchanger vary. The objective of the design is to select the configuration of the multi-component system such that the total enthalpy flow rate delivered to the heat pumps is larger and the total pumping power is smaller. The paper documents the effect of geometry (the connections) and the relative sizes (mass flow rates of heat pumps) on the total enthalpy flow rate. The paper shows the parametric domain in which the design with a single heat exchanger is superior in comparison with the classical design where each heat pump is connected to its own heat exchanger.