Hongfa Di

Experimental study on the thermal performance of the shape-stabilized phase change material floor used in passive solar buildings

The novel shape-stabilized phase change material (PCM) has the following salient features: large apparent specific heat for the phase change temperature region, suitable thermal conductivity, and the ability to keep the shape stabilized when it undergoes a phase change. In this technical brief, we put forward a kind of shape-stabilized PCM floor that is able to absorb solar radiation energy in the daytime and to release the heat at night in winter. The thermal performance of a prototype room using such a floor was studied. The experiments show that the mean indoor temperature of a room with the PCM floor is about 2°C higher than that of the room without a PCM floor, and the indoor temperature swing range is obviously minimized. Therefore, installing shape-stabilized PCM in a room may increase the degree of thermal comfort and reduce space heating energy consumption in winter In addition, the experimental results provide data for modeling and simulation research for such PCM floor systems.

Urban Building Energy Planning With Space Distribution and Time Dynamic Simulation

It is important to deal with energy saving in buildings of one city level, and plan the energy system from one building to one city level. We strongly suggest conducting urban building energy planning (UBEP) in the urban planning field in China. There are two main characteristics of an urban building energy system. First, the terminal building energy demand is dynamically timely. Second, the energy demand, energy sources supply, energy equipments, and networks of heating, cooling, gas, and electricity, are distributed in an urban space. It is meaningful to conduct an innovative urban energy planning with space distribution and time dynamic simulation. Therefore, an UBEP simulation tool, developed by our research group, is introduced. Finally, a case of energy planning in Beijing City in 2010 for heating and air conditioning system is dynamically simulated and analyzed. To meet the same building energy demand in Beijing, such as heating, air conditioning, gas, and electricity, different energy equipments, such as boiler, combined heating and power, combined cooling, heating, and power system, and heat pump based on different energy sources, such as coal, gas, and electricity, should be planned alternatively. Also, an optimum urban energy system with high energy efficiency and low environmental emission can be achieved. This simulation tool contains most models of heating and cooling energy systems in China. We can validate the models with statistical data from previous or present simulation, and the simulation results in future planning can serve as guidance for the construction of municipal energy infrastructure. We can conclude that simulation in time dimension shows the characteristics of dynamic load in each nodes of the energy flow. The objective is to present the comparison of different scenarios and optimize the planning schemes.

Experimental Study of Underfloor Air Supply System With Air Solar Collector and Shape-Stabilized PCM

In this paper, a new kind of solar energy heating system with shape-stabilized PCM is put forward. It can absorb the solar energy in the daytime and release the heat at night in winter. The solar radiation energy was gained by air solar collector, and the heated air was sent to the underfloor space of the room with ducts at daytime. Then the thermal energy was stored in the shape-stabilized PCM plates. The shape-stabilized PCM can keep the shape stabilized when PCM undergoes a phase change because it is microencapsulated by the supporting material. At night the heat energy stored in the PCM could be released into the room by the ductless air supply. The thermal performance of a room using such system was experimentally studied. The experiments show that the thermal comfort degree of solar buildings can be improved when applying shape-stabilized PCM suitably. The conventional space heating energy consumption in winter can be greatly saved. Besides, the experimental results provide the data for further modeling and simulation research of such kind of system.Copyright

Simple method of calculating the transient thermal performance of composite material and its applicable condition

Degree of mixing of composite material is defined and the condition of using the effective thermal diffusivity for calculating the transient thermal performance of composite material is studied. The analytical result shows that for a prescribed precision of temperature, there is a condition under which the transient temperature distribution in composite material can be calculated by using the effective thermal diffusivity. As illustration, for the composite material whose temperatures of both ends are constant, the condition is presented and the factors affecting the relative error of calculated temperature of composite materials by using effective thermal diffusivity are discussed.

The Energy Efficiency and Economic Feasibility Analysis of the Distributed Absorption Cooling Combined With District Heating System

The distributed absorption cooling based district heating system was investigated in order to utilizing the reject heat from the combined heat and power (CHP) plant in summer. Compared with the electric compressor cooling, the energy efficient and cost-effectiveness of the distributed absorption cooling were furthermore analyzed by the Fuel Energy Saving Ratio (FESR) method. The sensitivity of some variables, such as the average electric efficiency, heating and electric generation efficiency of the CHP system, and the coefficient of performance (COP) of the chiller, were analyzed. The marginal heating price of the distributed absorption cooling can be obtained. According to the evaluation results, the applicability of the distributed cooling with district heating system is limited by the lower energy efficiency and economical benefits. The approaches to increase the energy efficiency were suggested in this paper. The improved distributed absorption cooling combined with liquid desiccant dehumidification which has higher heating utilization efficiency was put forward and analyzed, and the energy efficiency evaluation results showed that the improved distributed cooling has higher energy efficiency and economical benefits, and great applicability.Copyright

Model and Simulation on Thermal Performance of Shape-Stabilized Phase Change Material Floor

Shape-stabilized phase change material (PCM) is a kind of novel PCM. It has the following salient features: large apparent specific heat for phase change temperature region, suitable thermal conductivity, no container. In the present paper, a kind of floor based upon shape-stabilized PCM is put forward which can adsorb the solar radiation energy in the daytime and release the heat at night in winter. Therefore, in winter the indoor climate can be improved and the energy consumption for space heating may be greatly reduced. A model of analyzing the thermal performance of this shape-stabilized PCM is developed. By using the model, the influence of various factors (thickness of PCM layer, melting temperature, heat of fusion, thermal conductivity of PCM etc.) on the thermal performance is analyzed. The model is verified with the experimental results. The model and the analysis are helpful for the application of shape-stabilized PCM based floor in solar energy buildings.Copyright

Experimental Research on Thermal Performance of Shape-Stabilized Phase Change Material Floor

Experimental study was conducted on the thermal performance and energy saving effect of a room with shape-stabilized phase change material (PCM). The results showed that the mean indoor temperature of the room with PCM floor was about 2°C higher than that of the room with normal floor and the indoor temperature swing range narrowed greatly. The results also manifested that by applying shape-stabilized PCM in room suitably, the thermal comfort level could be raised and space heating energy in winter could be saved. Finally, the experimental results enriched the database for the further modeling and simulation research.Copyright

EXPERIMENTAL RESEARCH ON HIGH- TEMPERATURE PHASE CHANGE THERMAL ENERGY STORAGE HEATER

The experimental research on the charging and discharging thermal energy performance of the electric heater is addressed. The results show that the heater has many merits: high thermal energy capacity; stable thermal performance; In order to enhance the heat dissipation during the discharging heat process, the experiment on the air passage is researched. The results show that the heater structure is reasonable; and its discharging rate of thermal energy can meet the need of heating.