薄型干式地板辐射供暖系统实验研究

本文建立了双层铝箔薄型干式地板辐射供暖的实验系统和样板间,在供暖期间测试了连续供暖和间歇供暖模式下室内空气温度、地板表面温度和热流密度的变化规律,并与数值模拟结果进行了比较。研究表明:本文提出的薄型干式地板构造与常规湿式低温热水地板辐射供暖地板构造相比,可有效降低地板构造层厚度、减小楼板荷载、节约建造能耗;地板表面温度分布均匀,向下传热比例小,向下热流密度占总热流密度的18.13%;薄型干式地板的供暖预热期少于2 h,可实现间歇供暖且停暖后室内空气温度仍可达到17℃;实验测试结果与数值模拟结果在误差允许范围内较吻合,为新型薄型干式地板辐射供暖系统地板的设计和工程应用提供了参考和依据。     

板式地板辐射供暖系统传热性能模拟研究

建立了板式地板辐射供暖的二维稳态传热模型。采用有限元分析软件ANSYS,分析了地板表面温度分布、传热计算单元内部温度分布、地板表面热流密度的影响因素及地板表面平均温度的影响因素,在考虑地板向下传热时对模拟计算结果进行了修正。供、回水平均温度是影响地板表面热流密度和平均温度的主要因素。当室内温度为20℃时,在维持适宜的地板表面平均温度范围24~28℃的前提下,供、回水平均温度的变化范围为27~34℃,考虑地板向下传热后,应控制在30~35℃。考虑地板向下传热后,应将模拟计算结果乘以一个不小于0.9的修正系数。     

预制轻薄相变复合供暖地板的构造与研究

提出了一种预制轻薄相变复合供暖地板,将相变材料渗入硅钙板构造层形成相变蓄热层。并采用ANSYS数值模拟软件对该相变复合供暖地板的传热性能进行了数值模拟,给出了地面表面温度和热流及其向下热损失,并对相变复合供暖地板进行了经济性分析。研究结果为地面辐射供暖技术的推广和应用提供了理论依据。     

数值模拟技术在多孔砖墙传热性能研究中应用

本文总结了多孔砖的数值设计优化步骤。通过例子介绍了多孔砖墙传热数值模拟过程,以及砖孔可视表面辐射的模拟和墙体表面温度、热流密度的计算方法,并给出了有关结果。     

低温地板辐射供暖的动态仿真

建立了低温地板辐射供暖系统传热过程的数学模型,通过数值模拟,用有限差分法计算了地板内的温度场。利用动态仿真程序预测了不同的供回水温度,埋管层厚度,盘管间距对地板传热过程,地板表面温度的影响,并在典型工况下,通过对理论值与实验值进行分析,验证了本模拟程序是正确的,该研究为地板辐射供暖系统的推广应用奠定了基础。     

强化对流式架空地板辐射供暖房间热环境特征研究

针对提出的强化对流式架空地板辐射供暖末端系统,采用数值模拟方法研究了地板表面温度与热流分布,以及供暖房间热环境特征,通过实验研究分析、验证了数值计算模型的可靠性。结果表明:强化对流式架空地板表面温度与热流分布规律主要受地板开孔数量、形状、位置等因素影响;盘管运行水温升高10℃时,地板表面温度升高2℃左右,室内平均温度升高2.8℃左右,架空地板表面热流密度增大约15 W/m~2;盘管间距每减小100mm,室内平均温度升高1.8℃左右;房间中间热源区域风速较小,在0.11~0.18m/s之间,满足工作区人员舒适性要求。     

地板辐射采暖结构层传热分析计算

建立了低温地板辐射采暖结构层二维稳态导热数学模型;采用有限差分法,对数学模型进行离散,利用Fortran语言编制了计算机的程序,并进行了数值模拟计算;分析了供回水平均温度、排管间距、填充层厚度、以及传热管径对地板表面温度及热流密度的影响。     

基于不同管径毛细管辐射顶板供冷性能模拟

建立三维毛细管辐射供冷顶板传热模型,利用CFD方法对不同毛细管管径下辐射顶板流动及传热进行数值模拟求解,以获取辐射顶板的供冷量及辐射表面温度分布状况。数值模拟得到的供冷量与ASHRAE手册中辐射供冷顶棚的传热理论计算结果相符,相对误差小于15%。数值研究表明,当毛细管管径在3~5mm的范围时,辐射顶板能保证良好的供冷性能,辐射表面温度分布均匀;管径大于5mm或者小于2mm,辐射板供冷量明显减少,辐射表面温度分布越不均匀。     

地板辐射采暖系统若干问题的研究

本文在分析低温热水地板辐射采暖系统传热规律的基础上,建立了地板辐射采暖系统的二维稳态传热数学模型;进而利用有限单元法对不同地面层材料及布置方式进行分析,求出了数学模型的数值解;最后给出并分析了地面层材质与厚度、管间距、管径、水温及室温等因素对地板地面温度和热流密度影响的定性及定量关系.对于地板辐射采暖系统的优化设计、安全可靠地运行具有一定的参考价值.     

低温地板辐射供暖特性参数的研究

建立了低温地板辐射供暖房间各围护结构的热平衡关系式，计算了地板表面温度、热流密度、室内空气温度和围护结构内表面温度。介绍了计算地板表面温度和围护结构内表面温度的耦合程序，测试了地板辐射供暖房间的特性参数。     

地表装饰材料和保温层性能对辐射地板热量损失影响的数值研究

建立了辐射地板供暖的传热模型，利用SIMPLER计算程序模拟计算了地表装饰材料和埋管保温层性能对辐射地板换热和地表温度分布的影响，得出了地板内部的温度场分布规律。研究结果表明，地表装饰材料对地板换热有很大的影响，埋管保温层对减少地板下层热量损失有十分重要的作用。     

地板辐射结构层表面温度的计算与分析

介绍了低温地板辐射供暖系统地板结构层传热模型,采用分离变量法推导出地板结构层温度分布的解析解,首次与相同模型下有限差分法求得的数值解进行比较,分析了不同因素对地表平均温度的影响。     

Optimum insulation for rectangular basements

The general solution of soil temperature variation is developed for a rectangular basement with a known heat flux distribution along the walls and the floor. The Interzone Temperature Profile Estimation (or ITPE) technique is applied to determine the steady-state variation of temperature within the ground. A water table at constant temperature is assumed to exist at a given depth below the soil surface. As an application of the general solution, the optimum thermal insulation distribution is determined for various basement configurations. A parametric analysis is conducted to determine the effect of basement depth and amount of heat flux required on the optimum insulation distribution along the surfaces of a rectangular basement.     

Foundation heat loss from heated concrete slab-on-grade floors

In recent years, there has been a renewed interest in heated concrete slab floors to provide for space heating in both residential and commercial buildings. The existing design procedures for these heating systems are based on simplified thermal models with several assumptions. In particular, the simplified models assume that both the upper and the lower concrete slab surface are isothermal and that the heat transfer through the bottom of the slab surfaces is uniformly distributed over the entire surface. In this paper, a more realistic and flexible model for heated or cooled concrete slab floors is considered to determine the heat transfer between the concrete slab and the ground. In particular, steady-state and steady-periodic semi-analytical solutions are developed to determine the temperature field within the ground medium and within the concrete slab-on-grade floor where hot or chilled water pipes are embedded. The solution presented in this paper is applied to determine the ground heat loss/gain for a heated or cooled floor under various design conditions including the level of floor insulation, and the temperature of the water pipes. These solutions are obtained using the interzone temperature profile estimation (ITPE) procedure. Detailed analysis is presented to determine the effect of the slab insulation configuration on soil and slab temperature field and on the monthly variation of the total slab heat loss.     

考虑衬砌和隔热层的寒区隧道温度场解析解

将隧道非齐次的瞬态传热分解为周期函数边界下的瞬态传热和恒温边界下的稳态传热,利用分离变量与Laplace变换相结合的方法,求解有保温隔热层的寒区隧道瞬态温度场的显式解析解。根据能量守恒,建立隧道洞内气体的气–固耦合传热模型,并获得洞内气体年平均温度和温度振幅的显式解析解。衬砌温度影响因素分析表明,随着隧道埋深和年平均气温的增加,二衬内、外两侧的温度呈线性增加,当年平均气温低于0℃,季冻区隧道埋深小于80m时,5cm厚隔热层很难单独满足防寒需求,应与主动供暖措施联合;随着隔热层厚度的增加,二衬的温度呈增长趋势,但增长速率却逐渐减小;当隔热层厚度超过5cm时,通过增加隔热层厚度来提高衬砌温度要考虑其经济性。依据隧址区的气候及地形条件,采用工程类比和解析解相结合的方法分段计算隔热层厚度。与实测值对比结果表明,理论解满足工程精度要求。     

Analytical solution for heat transfer in a multilayer floor of a radiant floor system

In radiant floor systems, the distribution of the floor surface temperature, which can be used to determine the mean temperature and the lowest/highest temperature of the floor surface, is an important parameter. The mean temperature of the floor surface determines cooling/heating capacity and indoor thermal comfort. The lowest surface temperature, which considers the dew point in an indoor environment, is a crucial factor in the prevention of condensation on a floor surface. The highest surface temperature is typically considered for local thermal comfort. In this paper, an analytical solution for heat transfer in a multilayer floor structure of a radiant floor system is proposed based on the analysis of the heat transfer process of a multilayer floor, equivalent thermal resistance and separation of variables method. The corresponding formulas are derived to estimate the distribution of floor surface temperature. The calculation results are validated by experiments. The calculation and experimental results show good accordance. The absolute error between the calculation and experimental results for floor surface temperature is within 0.3°C. A method for the calculation of the dimensionless temperature of the floor surface, which can be used for radiant heating and cooling systems, is provided. Using this proposed method, the distribution of floor surface temperature and the influence of floor structure parameters on the thermal performance of floors can be estimated and analyzed.     

A data analysis method for detecting wall thermal resistance considering wind velocity in situ

To improve the accuracy of data analysis methods for the field measurement of wall thermal resistance, a method considering wind velocity is presented through an analysis of both surface heat flux and temperature samples. This analysis method takes the wall heat transfer of linear system into account, simplifying the first order differential equation of wall transient response based on the nodes of the interior and exterior wall surfaces. An approximate solution has been proposed in the form of time domain interpolation. By applying the weighted residual method for the approximate solution, the data analysis method about temperature, heat flux, and wind velocity can be achieved.A transient heat transfer model of a wall was established applying the infinite difference method, by which the proposed analysis method was validated in this paper. Additionally, the heat flow meter experiment platform considering wind velocity was built, on which the proposed method, the mean method and the dynamic analysis method suggested by the international standard ISO 9869 were applied to the test wall under different wind velocities. The wall thermal resistance value obtained in our proposed method has proven to be in better agreement with that obtained for a steady state.     

Calculation of the steady-state heat transfer through a slab-on-ground floor

An analytic formula is derived for the steady-state heat transfer through a slab-on-ground floor, with and without thermal insulation, based on the solution of the fundamental heat transfer equation with relevant boundary conditions.

So far as the building dimensions are concerned, the heat loss depends only on a “characteristic length” of the floor, defined as the floor area divided by half the exposed perimeter, a result which greatly simplifies the expression of heat losses and their evaluation for a building of arbitrary shape. The heat transfer is restricted by the thickness of the external walls, surface resistance and by any applied thermal insulation. The influence of these factors is combined appropriately so as to permit the straightforward evaluation of the thermal transmittance of the floor for any wall thickness and insulation thickness.     

地板辐射采暖电加热管传热过程影响分析

通过分析电加热地板辐射采暖传热过程,建立电加热管传热模型,进行方程离散和数值模拟,并分析电加热地板辐射的发热电缆间距、地板面材料等因素对电加热管传热影响.研究结果表明:满足室内热环境条件相同时,地板面热流密度按从大到小依次是大理石、瓷砖、软木板;随着发热电缆间距的增大,地板面温度分布开始出现波动,热流密度逐渐降低,地板...