Small temperature difference terminals

Abstract

Air-source heat pump (ASHP), as an optional product, has already been extensively applied to residences and offices in hot summer and cold winter. However, the existing products confront serious problems under heating conditions in winter. A visible issue is that the air distribution is irrational because the terminals in room, in most cases, are installed in an upper space, which makes users feel uncomfortable. Another issue is that the terminals are designed under an inappropriate condition, leading to a low efficiency of the air-source heat pump. In addition, the terminals themselves are not designed with the best structure parameters and hence influence the heat transfer performance a lot. To solve the problems above, small temperature difference terminals (STDTs), such as small temperature difference fan-coil unit (STDFCU) or floor-heating coil (FHC), have been proposed. In this chapter, a small temperature difference fan-coil unit is designed and manufactured. Besides, its heat transfer performance is tested. An air-source heat pump combined with four selected prototypes is applied to a 100 m 2 apartment. The system performance and energy consumption in heating mode are measured. According to the results, the room environment can be kept in a comfortable state under the condition that the supply water is kept at 35 °C, which can lead to almost half reduction of energy consumption compared to the condition under which the supply water is kept at 45 °C. Finally, a larger air-source heat pump system is applied to a public building and the performances of STDFCU, and normal fan-coil unit (NFCU) in cooling mode are analyzed from several aspects, including their energy consumption and indoor temperature distribution in summer. Meanwhile, the performances of STDFCU, NFCU, and FHC in heating mode are analyzed including energy consumption and zone comfort in winter. The result shows that ASHP + STDFCU system can save 15-22% energy compared to traditional ASHP+NFCU system and thus has a 13-24% higher COP than ASHP + NFCU system depending on the weather condition in summer. What's more, STDFCU and FHC in heating mode can reduce system energy consumption up to 20%, and the air distribution in the room is more uniform in winter.