电热锅炉蓄热在空调采暖系统中的应用

介绍了电热锅炉蓄热的意义、系统形式及原理，在实例中对系统设计提出了新思路，并介绍了电热锅炉及蓄热槽的选型。     

住宅分户计量采暖系统与按热量计费技术的研究

对新型的分户热计量采暖系统的技术设计进行了定量和定性的多方案对比,提出了最佳的系统模式。为如何根据热表记录数值对各住户进行合理收费提出了一个科学可行的计算方法。     

Analytical solution of the inverse unsteady wall heat conduction problem and experimental application

Based on the analytical solution of the unsteady heat conduction differential equation, a solution procedure is presented for the inverse unsteady wall heat conduction problem, i.e. for the calculation of the thermal properties of structural elements of existing buildings under real transient conditions, using on-site temperature measurements. Previous procedures, which were based on the finite-difference method, required a considerable number of temperature measurements in space and time within the wall. The advantage of the present analytical procedure is that it requires only two temperature measurements, apart from some information on the outdoor and indoor temperature variations. The two temperature measurements may be taken on the outdoor and indoor wall surfaces at the same time level, or on one of these surfaces at two different time levels. The proposed analytical procedure provides the values of the thermal conductivity and heat capacity of structural elements, and therefore it may be used in practice for ex post checking of the materials used by the constructor, or for load calculation when heating or cooling systems are to be installed in old buildings of unknown wall properties. Experimental examples are presented which show that the proposed analytical procedure may be applied in practice with very good accuracy.     

住宅分户计量采暖系统与按热量计费技术的研究(续)

对新型的分户热计量采暖系统的技术设计进行了定量和定性的多方案对比,提出了最佳的系统模式。为如何根据热表记录数值对各住户进行合理收费提出了一个科学可行的计算方法。     

Analysis of thermal performance of electromagnetic induction based molten salt heating system

将电磁感应加热技术应用到低谷电加热熔盐储热供暖领域,搭建熔盐电磁感应加热实验系统,以感应加热器为研究对象,探究熔盐以及线圈冷却水在不同熔盐流速和线圈电流工况下的温度变化规律,计算加热效率和冷却水热损失率。结果表明：电磁感应加热器可以快速加热熔盐,熔盐温升主要集中在开始加热80～240 s之间,温升速率在100 s时最大;改变线圈电流或熔盐流速,可以产生不同终温的熔盐,流速0.177 m/s时,熔盐在不同电流下出口温度分别为201.452 ℃、203.891 ℃、207.599 ℃、212.975 ℃和221.454 ℃;熔盐流速一定,熔盐和线圈冷却水吸热量随线圈电流的增加而升高;线圈电流不变,熔盐吸热量随流速的增加而升高、线圈冷却水吸热量随流速增加而降低;熔盐流速0.296 m/s、线圈电流600 A时,熔盐加热效率为69.28%,线圈冷却水热损失率为16.45%。     

A thermal analysis of a radiant floor heating system using SERI‐RES

Both intermittent and continuous heating are widely used for radiant floor heating systems in Korea, Intermittent heating circulates hot water according to a predefined schedule while the continuous heating controls water flow using thermostat control units. The standard version of SERI‐RES has been modified for the numerical simulation of the problem. Results show relatively large temperature swings in the case of intermittent heating with solar availability, although it costs less to implement due to its simplicity in design. On the other hand, the case of continuous heating would avoid such undesirable temperature fluctuations. These results are also verified by experimental evaluations. Copyright © 1999 John Wiley & Sons, Ltd.     

Integration of solar air collector with phase change material wall for a heating system

可再生能源的高效利用是降低建筑能耗的有效方法。将相变储能墙与太阳能热风相结合,可改善太阳能热风采暖的不稳定性,从而提高太阳能的利用效率。通过试验和ANSYS模拟软件对复合系统的分析,确定相变储能墙体的储热特性和合理用量,研究复合采暖系统的室温变化和传热规律,分析相变储能墙对采暖系统的贡献率。结果表明：与未采暖房间相比,复合采暖系统可以使室内平均温度提高7~15℃,该复合采暖系统具有一定的应用前景;当太阳能空气集热器的送风口温度在37~77℃时,相变材料能够充分利用,相变墙整体的相变比例约为40%,从线性回归比例看,复合采暖效果要比太阳能热风采暖效果好。     

The adjoint-solution technique for the calculation of the thermal properties of layers in multilayer walls under transient heat conduction

The thermal properties of the layers of a wall, whether or not exposed to solar radiation, are calculated provided that the boundary conditions and some values of the transient temperature field within the wall are known. The developed procedure is based on the adjoint-solution technique and is applicable both to walls in operation and to the design of walls that are required to meet certain temperature specifications. In the former case, temperature measurements are needed. Theoretical and experimental tests have proved the accuracy of the method. Applications may be found in energy management and thermal storage in buildings, in the improvement of passive systems and in the design of multilayer slabs forming parts of heat-transfer equipment. © 1997 by John Wiley & Sons, Ltd.     

A modified zone model for estimating equivalent room thermal capacity

The zone model has been widely applied in control analysis of heating, ventilation and air conditioning (HVAC) systems to achieve a high building efficiency. This paper proposed a modified zone model which is much simpler in the HVAC system simulation and has the similar accuracy to the complicated simulation model. The proposed model took into consideration the effect of envelop heat reservoir on the room indoor temperature by introducing the thermal admittance of the inner surfaces of the building enclosure. The thermal admittance for the building enclosure was developed based on the building thermal network analytical theory and transfer function method. The efficacy of the proposed model was demonstrated by comparing it with the complicated model — heat balance method (HTB2 program). The predicted results from the proposed model well agreed with those from the complicated simulation. The proposed model can then make the HVAC system dynamic simulation much faster and more acceptable for control design due to its simplicity and efficiency.     

Thermal performance of a non-air-conditioned building with PCCM thermal storage wall

This paper presents a time-dependent periodic heat transfer analysis of a non-air-conditioned building having a south-facing wall of phase-changing component material (PCCM). A rectangular room (6 × 5 × 4 m) based on the ground is considered. The effects of heat transfer through walls and roof, heat conduction to the basement ground and furnishings, heat gain through window and heat loss due to air ventilation have been incorporated in the periodic time-dependent heat transfer analysis. The time-dependent heat flux through the PCCM south-facing wall has been obtained by defining the effective thermal properties of the PCCM for a conduction process with no phase change. Numerical calculations are made for a typical mild winter day (7 March 1979) at New Delhi for heat flux entering through the wall and inside air temperature. Further, a PCCM wall of smaller thickness is more desirable, in comparison to an ordinary masonry concrete wall, for providing efficient thermal energy storage as well as excellent thermal comfort in buildings.     

低温热水地板辐射与低温电热地膜辐射供热方式的特性分析

主要对低温热水地板辐射与低温电热地膜辐射供热方式进行分析。分析了低温热水地板辐射与低温电热地膜辐射两种供热系统的节能特性及其适应性;两种供热系统存在的问题及及其在集中供热中的应用发展前景。     

A model of the thermal restoration transient state of an opaque wall after the interruption of solar radiation

The temperature distribution of an outer wall of a room subjected to solar radiation goes through a transient state until it reaches a thermal equilibrium state. After an interruption of solar radiation, the temperature profile on the wall cross-section, starting from the latter thermal equilibrium state, returns through a transient state to the initial thermal equilibrium state. The transient state between the above two equilibrium states is called the thermal restoration transient state of the wall. The duration of the thermal restoration transient state depends on the structural characteristics of the wall and on the thermal parameters of the room–environment system. The influence of the thermal restoration transient state on the evaluation of the ability of an opaque wall to store and exploit solar radiation and on the computation of the resulting thermal gain of the room during the thermal restoration of the wall is important, because it acts as a flywheel. In the present work analytical expressions yielding the temperature profiles and the duration of the transient state as a function of thermal and structural characteristics have been developed. An analytical model for the thermal gain of the room during the thermal restoration of the wall also was developed. An experimental verification of the duration of the transient state of the thermal restoration was made.     

Thermal performance of PCM thermal storage unit for a roof integrated solar heating system

The thermal performance of a phase change thermal storage unit is analysed and discussed. The storage unit is a component of a roof integrated solar heating system being developed for space heating of a home. The unit consists of several layers of phase change material (PCM) slabs with a melting temperature of 29 °C. Warm air delivered by a roof integrated collector is passed through the spaces between the PCM layers to charge the storage unit. The stored heat is utilised to heat ambient air before being admitted to a living space. The study is based on both experimental results and a theoretical two dimensional mathematical model of the PCM employed to analyse the transient thermal behaviour of the storage unit during the charge and discharge periods. The analysis takes into account the effects of sensible heat which exists when the initial temperature of the PCM is well below or above the melting point during melting or freezing. The significance of natural convection occurring inside the PCM on the heat transfer rate during melting which was previously suspected as the cause of faster melting process in one of the experiments is discussed. The results are compared with a previous analysis based on a one dimensional model which neglected the effect of sensible heat. A comparison with experimental results for a specific geometry is also made.     

Thermal restoration of a wall after the interruption of solar radiation flux

The transient phenomenon of the thermal restoration of an opaque wall of a room after the interruption of solar radiation flux was analysed. The wall, was initially, in thermal equilibrium under solar radiation. When the solar radiation flux was interrupted, the temperature distribution on the wall cross-section went through a transient state until it reached a final equilibrium state. During the thermal restoration of the wall, a thermal gain is maintained for the room as a result of the exploitation of a part of the thermal energy stored in the wall. Analytical expressions have been obtained for the duration of the thermal restoration, for the thermal gain of the room during this transient state and for the coefficients of storage and exploitation of the solar radiation by the wall.     

A study on thermal conductivity of a mixture of magnesia particles and molten nitrate by a transient hot wire method

In this study, the effective thermal conductivity of a mixture of magnesia particles and molten nitrate used in a high temperature thermal energy storage system was investigated by a transient hot wire method. The effective thermal conductivity of the mixture was around 2.0W/(m·K) in the temperature range of 423 K to 703 K, although it decreased about 5% with increasing temperature. This value was about 10 times larger than that of the packed bed of magnesia particles including air. The effective thermal conductivity increased about 3% with a 1% increase in the volume ratio of magnesia particles in the mixture with molten nitrate. © 2006 Wiley Periodicals, Inc. Heat Trans Asian Res, 35(4): 245–253, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20116     

Analysis of a solar water heating system with n-tanks in series

A straightforward analysis of a solar water heating system with n-tanks connected in series has been presented. The long-term performance of the system has also been studied. On the basis of numerical calculations made for four successive days, the following conclusions have been drawn:

1. (1) The fluctuation in temperature variation decreases with increase of the number of tanks connected in series.

2. (2) The variation becomes smooth after the second successive day, which is more desirable from the point of view of users.

     

Study on key parameters design and economic evaluation of the electric heating and solid sensible heat thermal storage device

电制热固体储热系统对可再生能源消纳、能源清洁化利用具有重要意义。电制热固体储热装置的关键参数设计以及经济性分析是提高经济效益的重要手段。因此,本文提出了电制热固体储热装置投资运行费用计算方法。通过对比不同供暖方式所需费用分析了电制热固体储热装置的经济性。同时研究了谷电利用系数对电制热固体储热装置经济性的影响。最后,采用案例分析验证本文所提经济性评估方法的合理性与正确性。本文的研究内容为用户对电制热固体储热装置的选择提供参考。     

Investigation of a combined solar–heat pump system for residential heating. Part 1: experimental results

In order to investigate the performance of the combined solar–heat pump system with energy storage in encapsulated phase change material (PCM) packings for residential heating in Trabzon, Turkey, an experimental set‐up was constructed. The experimental results were obtained from November to May during the heating season for two heating systems. These systems are a series of heat pump system, and a parallel heat pump system. The experimentally obtained results are used to calculate the heat pump coefficient of performance (COP), seasonal heating performance, the fraction of annual load meet by free energy, storage and collector efficiencies and total energy consumption of the systems during the heating season. Copyright © 1999 John Wiley & Sons, Ltd.     

某天然气净化厂供热系统设计

某天然气净化厂需设置一套供热系统,为工艺装置及冬季采暖提供热负荷.根据热用户对用热参数的要求,可采用蒸汽锅炉供热系统或导热油加热炉供热系统.从投资、运行、管理及维护等方面对两种供热系统进行方案比较.导热油加热炉供热系统具有以下优点:运行和维护费用低、不消耗水资源、可露天布置、导热油倾点低,适合当地严寒气象条件.推荐选用...     

Monitoring of transient 3D temperature distribution and thermal stress in pressure elements based on the wall temperature measurement

Abstract

Two methods for monitoring the thermal stresses in pressure components of thermal power plants are presented. In the first method, the transient temperature distribution in the pressure component is determined by measuring the transient wall temperature at several points located on the outer insulated surface of the component. The transient temperature distribution in the pressure component, including the temperature of the inner surface is determined from the solution of the inverse heat conduction problem (IHCP). In the first method, there is no need to know the temperature of the fluid and the heat transfer coefficient. In the second method, thermal stresses in a pressure component with a complicated shape are computed using the finite element method (FEM) based on experimentally estimated fluid temperature and known heat transfer coefficient. A new thermometer with good dynamic properties has been developed and applied in practice, providing a much more accurate measurement of the temperature of the flowing fluid in comparison with standard thermometers. The heat transfer coefficient on the inner surface of a pressure element can be determined from the empirical relationships available in the literature. A numerical-experimental method of determination of the transient heat transfer coefficient based on the solution of the 3D-inverse heat conduction problem has also been proposed. The heat transfer coefficient on the internal surface of a pressure element is determined based on an experimentally determined local transient temperature distribution on the external surface of the element or the basis of wall temperature measurement at six points located near the internal surface if fluid temperature changes are fast. Examples of determining thermal and pressure stresses in the thick-walled horizontal superheater header and the horizontal header of the steam cooler in a power boiler with the use of real measurement data are presented.