Storage devices for heat exchangers with phase change

• A combination of swappable storage devices with heat exchangers is proposed.
• The storage devices reduce the temperature spreads in the heat exchangers.
• With reduced spreads, efficiency increases of heat exchangers are achievable.
• The authors present the working principle of the devices and the theoretical background.
• A prototype implementation with measurement results is illustrated

Heat exchangers with phase-change achieve minimal dissipation when there is only a small temperature difference between the inlet and the outlet on the side of the sensible heat transfer medium. However, this does not usually occur in applications where these heat exchangers are typically used. In order to overcome this issue, an innovative prototype heat pump was realised. The heat pump was equipped with switchable storage devices to adapt the high temperature difference of the application to small temperature differences in the condenser. This way, the dissipation in the condenser was minimised, which led to COP increases by reducing the required mean pressure in the condenser. The use of storage devices resulted in measured efficiency improvements of 10%–50% in the prototype. With the described set-up, it is possible to approach the maximal thermodynamically possible COP, which makes an adaptation of the theoretical assessment of heat pumps necessary.