Search

This paper presents an experimental study on a bilinear temperature control of a ground source heat pump (GSHP) integrated variable air volume (VAV) air-conditioning system, which may experience significant variations in the supply air temperature due to the frequent on/off switch of the ground source heat pump and the low thermal capacity at the air side. The bilinear control was realized in a building automation system (BAS) and applied to a test rig. The experimental results show that with an online estimation of the cooling load the bilinear control was able to maintain the space temperature at its set-point well and the control performance was superior to that of a conventional PI control. Therefore, the bilinear control has the potential to be used in GSHP integrated air-conditioning systems to improve the robustness and accuracy of the space temperature control. [ABSTRACT FROM AUTHOR]

Abstract: Heat pumps could be used to produce hot water for hybrid cooling towers for preventing the occurrence of plume in subtropical regions. The evaporative side of the heat pump system could be arranged either at the inlet side or at the outlet side of these cooling towers for cooling down the cooling water temperature. Alternatively, the evaporative side of the heat pump system could also be arranged at the evaporative side of chillers to reduce return chilled water temperature and therefore to reduce the cooling load of chillers. This study presents the evaluation of the impacts of these three arrangements of the heat pump system on the plume control performance and the energy performance in a large-scale chiller plant in Hong Kong. The performance prediction and evaluation of the chiller plant and the plume abatement system were conducted on a dynamic simulation platform. The results show that these three arrangements have almost the same plume control performance with sufficient plume control capability. The results also show that the arrangement of the evaporative side of the heat pump system for cooling down return chilled water temperature has much better performance that the other two arrangements for improving the overall energy efficiency. [Copyright &y& Elsevier]

Radiant cooling is an energy-efficient space cooling technology in built environments to achieve high thermal comfort. However, there are technical bottlenecks of condensation risk and insufficient cooling capacity in hot and humid climates. The use of double-skin infrared-transparent membranes (DIMs) to separate the radiant cooling surface from the air-contact surface can improve the cooling capacity while preventing condensation. Current research focuses on theoretical analysis and reduced scale experiments, and the lack of measured operational and performance data creates a key limitation on DIMs use. Therefore, the verification of radiant cooling system with DIMs in a full-scale experimental space and its radiant cooling performance need to be further studied. In this study, two full-scale radiant cooling chambers (one with DIMs and one without DIMs) were constructed. The effect of DIMs on radiant cooling performance was studied by monitoring surface temperature, condensation risk and cooling capacity. The results indicated that the air-contact surface temperature in radiant cooling with DIMs was always maintained above the dew point temperature for condensation-free safety at a low water supply temperature of 8 °C. In contrast, the conventional radiant cooling without DIMs had severe condensation. Moreover, the cooling capacity of radiant cooling panel with DIMs was 105.5 W/m2 at water supply temperature of 8 °C, 24.4 % improved compared to radiant cooling panel without DIMs at water supply temperature of 14 °C. This study provides prototype experimental verification for new technology with DIMs to improve radiant cooling performance and provides experimental data as a reference for related theoretical and model studies. [ABSTRACT FROM AUTHOR]

Highlights: [•] Sensitivity analysis of energy performance is performed for residential envelope. [•] EETP method is introduced to calculate cooling and heating energy use. [•] Shading coefficient and window to wall ratio are the most vital factors in summer. [•] Wall heat transfer coefficient and shape coefficient have crucial effect in winter. [•] Wall heat transfer coefficient and window to wall ratio weight the most in a year. [ABSTRACT FROM AUTHOR]