Experimental research on performance of the solar heat gain (SHG) insulation panel

Recently, research on energy efficiency for buildings has been performed due to a shortage of energy and increased concern about the environment. Building envelopes have vital roles in energy efficiency. Insulation depth, opening designs, double skins and other methods have been discussed to improve the performance of building envelopes. Among these methods, the use of opaque insulation has a role for blocking the inner heat loss, but also for inefficiently blocking the natural solar heat coming to the inside of a building. This paper looks at a way of bringing solar heat to the inside of a building, which is impossible with normal insulation. The research measures the amount of heat gain and provides the possibility of energy savings through solar heat in a test building.     

Effect of roof solar reflectance on the building heat gain in a hot climate

The effect of the roof solar reflectance on the thermal performance of a building is often ignored. However, there are significant differences in heat gain from light and dark-coloured roof surfaces. In this paper an equation for the average daily downward heat flow of a sunlit roof is derived. Using building simulation, it is first shown that the thermal mass of the roof does not significantly affect the overall daily heat gain (although it causes a time lag and reduction in peak heat flow). As a consequence the daily heat gain from the roof may be estimated by integrating the equation for the steady-state downward heat transfer over the day. For north Australia the derived equation suggests that a light-coloured roof has about 30% lower total (air temperature difference and solar-driven) heat gain than a dark-coloured one. The effect of aging (change in solar reflectance with time) is considered in the calculations and a relationship between the solar absorptance of new and aged material is suggested. A classification of roof colours with respect to their solar absorptance (dark, medium, light and reflective) is proposed to enable a quick and simple assessment of the effect of roof colour on the heat gain and R-value.     

Effect of courtyard proportions on solar heat gain and energy requirement in the temperate climate of Rome

The present study focuses mainly on the effect of solar heat gain on the energy demand of courtyard building form with different proportions. Several methods can be employed to improve the building's utilization of solar heat gain. This includes using light colours for the external surfaces to reduce the solar radiation absorption in summer, using shading devices and improving the thermal properties of the external walls and roof. However, it is of great importance before using any of these methods to have the courtyard building's architectural design adapted to have full advantage of the available solar heat gain. Therefore, the main objective of the present examination was to find out to what extent the building's solar heat gain and consequently the energy requirements are influenced by the building's configurations. A computer Tool (IES) was used to carry out the investigation taking Rome as an empirical background to temperate climate. The results showed that the proportions of the courtyard building considerably influence the need for heating and cooling.     

Study on the performance of a solar assisted air source heat pump system for building heating

This paper proposed a new solar assisted air source heat pump system with flexible operational modes to improve the performance of the heating system. A mathematical model was established on the solar assisted air source heat pump system for building heating with a heating capacity of 10 kW, and an air source heat pump unit was developed to validate the model. The effect of the solar collector area on the performance of the system running in Nanjing was studied. The results showed that the COP of the heat pump unit was enhanced with the increase of the solar radiation density during the typical sunny day in the heating season. In addition, the COP also increased in proportion to the solar collector area. Compared with the case when the solar collector area was 0 m², the COP increase of the heat pump and the energy-saving rate were 11.22% and 24% respectively when the solar collector area was 40 m². Meanwhile, the solar equivalent generation power efficiency could reach 11.8%.     

太阳能热泵多功能复合机实验系统建模与仿真分析

本文简要介绍了太阳能热泵多功能复合机(SAHPM)制热系统的工作原理,建立了系统各主要部件的数学模型。考虑到仿真计算的实用性和稳定性,对冷凝器和蒸发器采用分区集总参数法建模,对压缩机和毛细管建立了稳态集中参数模型,给出了太阳能集热器能量平衡方程,通过对仿真结果和实验测试结果的对比分析,验证了模型的正确性。     

工程型太阳能热泵热水系统开发及产业化

为满足太阳能热利用规模需求,按模块化思路研制了一种工程型太阳能热泵热水系统产品,选用空气源热泵作为提供辅助能源的设备,提出了技术实现方案及智能化控制策略,开发了热泵机组、集热单元、储热单元、中央控制仪等装置和设备。通过试验优化了系统的匹配特性,提高了综合能效比及可靠性,实现了全部设备的集中控制和实时监测。进行了详细的技术经济分析,明确了产品的适用范围。     

建筑围护结构传热得热量计算方法的比较

比较了围护结构传热得热量的两种计算方法:周期性反应系数法和传递函数法。与传递函数法相比,周期性反应系数法简化了计算,而且周期性反应系数能反映围护结构对周期性扰量的热响应,可作为评价围护结构热稳定性的指标。推导了传递函数系数与周期性反应系数间的关系式,可根据ASHRAE的数据库RP 626建立典型围护结构周期性反应系数的数据库,从而减少周期性反应系数法的计算量。     

中高温热泵辅助太阳能三联供系统的实验研究

本文建立了利用中高温热泵作为辅助方式的太阳能三联供实验系统,开发了基于触摸屏操作的系统数据采集及运行监控系统(SCADA),并进行了采暖性能实验。结果表明,在12月份每天10:00￣14:00范围内,太阳能可以单独进行采暖,其它时间需要辅助,高温水箱在正常运行时温度一般都维持在45℃左右,12月份实验系统的太阳能保证率为64.6%。在3月份太阳能一天的蓄热量可以达到83.5kWh,热泵工作的性能系数为4.21。     

建设工程招投标阶段造价控制探讨

招投标是建立公开、公平、公正和诚实信用的市场秩序的有效手段,也是开展资源节约型经济活动,实现资源配置,提高资产投资效益的重要途径。本文即通过分析建设工程招投标的特点及招投标阶段对工程造价的影响,提出在招投标阶段涩制工程造价应采取的措施,从而达到有效控制工程造价的目的。     

人体显热散热冷负荷系数的完善

通过详细计算，给出了不同围护结构类型房间完整的人体显热散热冷负荷系数数据。     

An effective, low-cost mechanism for direct drag force measurement on solar concentrators

An effective technique for measuring the drag force on a solar concentrator in a subsonic wind tunnel with a simply-fabricated, low-cost force sensing mechanism is described. The measurement uncertainty was reduced by ensuring operation near full scale of the load sensor employed, and by averaging a large number of samples to reduce chance variations due to turbulent fluctuations in the system. The resulting drag coefficients from our apparatus successfully duplicated previously published experimental data from a geometrically-similar, parabolic trough style solar collector.     

大连某海水源热泵区域供热系统的实测分析

根据现场实测数据,分析了热泵机组及整个热泵区域供热系统的能效情况。结果表明,海水源热泵机组在冬季海水温度极低的情况下仍可运转,但机组的制热性能系数很低(约为2.43),系统整体的制热性能系数则更低(测试平均值为1.86)。进一步分析了影响机组制热性能的因素。模拟计算发现,若选择市场上性能优良的热泵机组,其制热性能系数将提升34.2%,系统整体能效可提升约24.2%。     

An accurate calculation model of solar heat gain through glazed surfaces

A model for the calculation of solar heat gain through glazed surfaces, to be used in the simplified calculation of thermal energy requirements in air-conditioned buildings, is proposed. The model uses the effective absorption coefficient of the indoor environment to take into account that the entering energy is in part absorbed by the surfaces of the cavity and in part is dispersed outwards, through the same glazed surfaces. The effective absorption coefficient is calculated by means of a correlation, and is made to depend on the average absorption coefficient of the internal opaque surfaces of the environment, on the glazed fraction and on the transmission coefficient of diffuse radiation of the glazed system. This coefficient permits a more accurate evaluation of solar heat gain through glazed surfaces, obtained adding: the direct optical contribution, produced by solar radiation absorbed by the indoor environment, the direct secondary contribution, produced by external solar radiation absorbed by the glazed surfaces, the indirect secondary contribution, produced by the absorption of reflected radiation exiting the indoor environment. The model, validated by means of comparisons with the TRNSYS 16 code, was used for the verification of the monthly solar heat gain calculation procedure of EN ISO 13790:2008.     

A laboratory experiment on natural ventilation through a roof cavity for reduction of solar heat gain

The study targets the reduction of roof solar heat gain through the use of natural ventilation in a roof cavity. This study is mainly concerned with factory buildings. Experimental outcomes were obtained from an inclined cavity model which was heated on the upper surface to mimic solar radiation on a roof. The dimensions of the cavity were 4882 mm× 400 mm × 78 mm. The two opposing smallest sides were allotted as the inlet and outlet, and narrowed to simulate resistance of the air flow in practical applications. Temperature and velocity measuring facilities were prepared in the experimental model. A number of measurements were carried out by varying the combinations of different heat production, inclination angles, and opening ratios. It was found that resistance to heat and air flow in the cavity was strongly influenced by the opening size. When the Reynolds number was examined, it showed that the flow belonged to the laminar region. The average velocity reached to 0.25 m/s at the highest in the examined cases. In other words, the cavity air was turned over 184 times in an hour. Natural ventilation in the roof cavity seemed to be effectively applicable to solar incidence discharges in factory buildings.     

Build-up and performance test of a novel solar thermal roof for heat pump operation

Global increase in energy demand and fossil fuel prices loaded ever-increasing pressure on identifying and implementing new means to utilise clean and efficient energy resources. Due to the environmental benefits, technical and economic possibilities of Solar-Assisted Heat Pump Systems, there has been a growing interest for such hybrid systems with a variety of system configurations for various climates. International Energy Agency Task 44 of the Solar Heating and Cooling Programme has recently started working on finding methods to most effectively use solar heat pump systems for residential use. In the present study, a novel solar thermal roof collector was developed by primarily exploiting components and techniques widely available on the market and coupled with a commercial heat pump unit. The proposed indirect series Solar-assisted Heat Pump system was experimentally tested and system performance was investigated. Yet, the analysis based on indoor and outdoor testing predominantly focuses on the solar thermal roof collector. A detailed thermal model was developed to describe the system operation. Also, a computer model was set up by using Engineering Equation Solver to carry out the numerical computations of the governing equations. Analyses show that the difference in water temperature could reach up to 18°C while maximum thermal efficiency found to be 26%. Data processing of the series covering the test period represents that Coefficient Performance of the heat pump (COP_HP) and overall system (COP_SYS) averages were attained as COP_HP?=?3.01 and COP_SYS?=?2.29, respectively. An economic analysis points a minimum payback period of about three years for the system.     

Dynamic performances of solar heat storage system with packed bed using myristic acid as phase change material

This paper is aimed at analyzing the thermal characteristics of packed bed containing spherical capsules, used in a latent heat thermal storage system with a solar heating collector. Myristic acid is selected as phase change material (PCM), and water is used as heat transfer fluid (HTF). The mathematical model based on the energy balance of HTF and PCM is developed to calculate the temperatures of PCM and HTF, solid fraction and heat release rate during the solidifying process. The latent efficiency, which is defined as the ratio between the instantaneous released latent heat and the maximum released heat, is introduced to indicate the thermal performances of the system. The inlet temperature of HTF (50 °C), flow rate of HTF (10 kg/min) and initial temperature of HTF (66 °C) were chosen for studying thermal performances in solar heat storage system. The influences of inlet temperature of HTF, flow rate of HTF and initial temperatures of HTF and PCM on the latent efficiency and heat release rate are also analyzed and discussed.     

北京地区居住建筑太阳能与地埋管热泵系统供热综合应用分析

本文针对北京地区居住建筑的具体情况和要求,在常规太阳能热水系统和地埋管热泵系统的基础上,提出了用于居住建筑供热的太阳能与地埋管热泵系统供热综合应用系统,并对系统流程与控制策略进行了分析,给出了该系统的使用条件和范围。本文为该系统的推广和应用提供了基础,有利于进一步在建筑中推进可再生能源技术的应用。     

Introduction to control of solar gain and internal temperatures by thermal insulation, proper orientation and eaves

In desert regions, the orientation of buildings, thermal insulation and eaves have an important influence in the inside air temperature. The main objective of the current work is to minimize interior temperatures by these three techniques. This study aims at assessing also the geographic parameter enhancing or damping the role of thermal inertia, providing a variety of results.As result, this work proves that stones play a contradictory role on thermal comfort; it has been found that changing orientations of building is not beneficial in terms of thermal comfort particularly in the hot season in case of a building without insulation. Consequently, the insertion of the eaves is recommended to achieve a better thermal comfort in arid and semi arid regions and the habitation will have to be situated in south flan of a hill to satisfy the two strategies (hot and cold).     

Design of a solar absorption cooling system in a Greek hospital

Air conditioning of buildings is responsible for a large percentage of the greenhouse and ozone depletion effect, as refrigerant harmful gases are released into the atmosphere from conventional cooling systems. The need to implement advanced new concepts in building air conditioning systems is more crucial than ever today.Solar cooling systems (SCS) have the advantage of using absolutely harmless working fluids such as water, or solutions of certain salts. They are energy efficient and environmentally safe. They can be used, either as stand-alone systems or with conventional AC, to improve the indoor air quality of all types of buildings. The main goal is to utilize “zero emissions” technologies to reduce energy consumption and reduce CO₂ emissions.Amongst cooling technologies, absorption cooling seems to have a promising market potential.In this paper, the performance and economic evaluation of a solar heating and cooling system of a hospital in Crete, is studied using the transient simulation program (TRNSYS). The meteorological year file exploited the hourly weather data where produced by 30-year statistical process. The required data were obtained by Hellenic National Meteorological Service.The objective of this study is to simulate a complete system comprised of a solar collector, a storage tank, a backup heat source, a water cooling tower and a LiBr-H₂O absorption chiller. The exploitation of the results of the simulation provided the optimum sizing of the system.     

太阳能空调及供热综合系统

结合建于山东的一个工程实例，介绍了太阳能吸收式空调及供热综合系统的构成、设计特点和主要性能，指出了太阳能空调的推广应用前景及目前尚待解决的问题。