Water Loop Heat Pump System Research Articles

Thermal performance and energy saving effect of water-loop heat pump systems with geothermal

Water-loop heat pump (WLHP) systems are an important option for space conditioning of commercial buildings. They provide the opportunity of saving energy through heat recovery and thermal balancing when heating and cooling occur simultaneously. WLHP systems typically operate with a loop water temperature of between 16 and 32°C. When cooling loads dominate, loop water temperatures are maintained below 32°C by rejecting excess heat with a cooling tower. When heating dominates, loop water temperatures are maintained above 16°C by a heater input. The emphasis of this paper is on the analysis of system performances, energy savings of the mixed cooling and heating mode of the WLHP systems, for it is a unique operating mode in air-conditioning and space heating systems. The energy saving effect by using low temperature geothermal energy as the heat input for WLHP systems was examined.

Energy start-stop and fluid flow regulated control of multizone HVAC systems

Temperature control of multizone indoor environmental spaces heated by a water-loop heat-pump system is studied. The system consists of a boiler, an evaporative cooler, heat pumps, a storage tank and environmental zones. An analytical model for the system is developed and a multivariable control strategy, which consists of both start-stop and integral mode controllers, is designed. Results showing the closed-loop system response subject to changes in heating and cooling loads are given.

Start-stop control strategies for heat recovery in multi-zone water-loop heat pump systems

A study is made to determine the energy saving potential of a start—stop controlled water-loop heat pump (WLHP) system. The physical model consists of individual heat pumps for each zone, a two-pipe water-loop system (with and without a storage tank), a boiler and an evaporative cooler. The overall system consists of four input energy controllers and an equal number of mass flow rate controllers. A simple start-stop control strategy for the system is developed. Results showing the typical daily operation of the system under changing heating and cooling loads are presented. A method for selecting the appropriate limits for loop water temperature which results in energy savings is given.