A solar heating system (SHS) with a phase change material (PCM) thermal storage tank is proposed with the view that traditional heat water storage tanks present several problems including large space requirements, significant heat loss and unstable system performance. An entire heating season (November–March) is selected as the research period on the basis of numerical models of the SHS-PCM. In addition, taking a public building in Lhasa as the object, the heating conditions, contribution rate of solar energy, and overall energy-saving capability provided by the heating system are analyzed under different PCM storage tanks and different terminal forms. The results show that an SHS with a PCM tank provides a 34% increase in energy saving capability compared to an ordinary water tank heating system. It is suggested that the design selection parameters of the PCM storage tank should specify a daily heat storage capacity that satisfies 70~80% of the entire heating season. A floor radiant system with supply/return water temperatures of 40/35 °C provides the optimal operation and the largest energy saving capability.

A physical model and dynamic simulation models of a solar phase-change heat storage heating system with a plate solar collector, phase-change material (PCM) storage tank, plate heat exchanger, and auxiliary heat sources were established. A control strategy and numerical models for each of seven different operation modes that cover the entire heating season of the system were developed for the first time. The seven proposed operation modes are Mode 1: free cooling; Mode 2: reservation of heat absorbed by the solar collector in the PCM storage tank when there is no heating demand; Mode 3: direct supply of the heating demand by the solar collector; Mode 4: use of the heat absorbed by the solar collector to meet the heating demands, with the excess heat stored in the PCM storage tank; Mode 5: use of heat stored in the PCM storage tank to meet the heating demands, Mode 6: combined use of heat stored in the PCM storage tank and the auxiliary heating sources to meet the heating demands; and Mode 7: exclusive use of the auxiliary heat sources in order to meet the heating demands. Mathematical models were established for each of the above seven operation modes, taking into consideration the effects of the outdoor meteorological parameters and terminal load on the heating system. The real-time parameters for the entire heating season of the system with respect to the different operation modes can be obtained by solving the simulation models, and used as reference for the optimal design and operation of the actual system.

Water tank is a commonly used unit which has been frequently applied for thermal energy storage units. In order to enhance the thermal performance of the water tank, the phase change material is utilized by embedding paraffin into water tank. But the key question is whether a competitive charging could be achieved. Therefore, an experimental system has been constructed. In this article, two key indices, the energy storage capacity and the energy storage intensity, are investigated. The performances of the phase change material–thermal energy storage tank during the heat charging processes are investigated experimentally, and a series of experiments are carried out under different heat transfer fluid flow rates and distance between phase change material plates. The temperature evolutions of the phase change material plates and heat transfer fluid are obtained during the experiments. The thermal performance of the phase change material–thermal energy storage tank was observed to be more effective than the conventional sensible thermal energy storage tank. It is found that water flow rate of 1.3 m³/h is taken as the optimal working condition, and the 3-cm plate distance is considered as the optimal design.

This paper gives a brief description of the over quick urbanization sinceChongqing, one of the biggest cities in China, has been a municipality directly under theCentral Government in 1997, excessive development and exceeding increase of high-risebuildings because of its special geographical position which finally leads to the worseningof the urban outdoor thermal environment. Then, this paper makes a bright balance to thefield measurement and simulated results of the wind speed field, temperature field of onemultifunctional high-rise building in Chongqing university located in the city center, andthe contrasted results validate the correctness of CFD in the outdoor thermal environmentalsimulation, expose the disadvantages of high-rise buildings on the aspects of blocking thewind field, decreasing wind speed which results in accumulation of the air-conditioningheat revolving around and periscian region where sunshine can not rip into. Finally, inorder to improve the urban outdoor thermal environment near the high-rise buildingsespecially for the angle of natural ventilation, this paper simulates the wind environment indifferent architectural compositions and architectural layouts by CFD, and the simulatedresults show that freestyle and tower buildings which can guarantee the wind speed andtake the air-conditioning heat away are much suitable and reasonable for the specialChongqing geography. These conclusions can also be used as a reference in othermountain cities, especially for the one with a great number of populations.

The heat source tower (HST), as a cleaner energy production, which can absorb the low-grade energy from ambient air to drive the heat pump unit without emissions has attracted more and more interest. In addition, HST has excellent economic applicability by using cooling tower equipment, which was idle in winter. However, there are few studies on comparative analysis of thermal behavior between counter-flow and cross-flow HST. A mathematical model suitable for both HST types was developed to identify the performance discrepancies between them. Then a parametric study was carried out in order to investigate the impact of solution and air as well as packing material properties on energy transfer of HSTs. Finally, the characteristics of solution dilution and dehumidification were investigated. As the inlet solution temperature increases, increases first, then decreases gradually, but a transition point occurs in the solution at −5 °C. Moreover, the transition section of moisture transfer direction for counter-flow HST was located in the 0.78 m and 0.26–1.56 m of packing material height, under the condition that the air relative humidity was 50%. In summary, this work intuitively indicates the thermal performance difference between counter-flow and cross-flow HST, also could assist the selection of proper operating conditions in HSTs.