ABSTRACT

A comprehensive understanding of the heat transfer mechanism of hydronically-heated structures is crucial to predicting their heating performance. However, few studies considered the heat transfer at the interface of heating pipe and host material. In this paper, heat transfer at two critical interfaces for hydronically-heated concrete structures, e.g. pipe-concrete interface and concrete-air interface, has been tested and analyzed. Two concrete blocks, one with an embedded cross-linked polyethylene (PEX) pipe and one with an attached PEX pipe, were fabricated to represent heated bridge decks for the heat transfer study. The two blocks were tested inside a freezer box in a series of heating response tests at varied room and fluid temperatures. Measured temperatures at different depths were used to find the convection heat transfer coefficient and the thermal contact conductance between the concrete and PEX pipe through equations developed via finite difference method (FDM). Finite element models (FEM) of the two blocks were developed to verify the thermal contact values derived from a 1-D thermal resistance model. A comprehensive analysis of the temperature response of the models was performed, especially at the two interfaces, and the FEM models were able to predict the lab measurements accurately. The obtained contact heat transfer coefficient and the FEM models can be used for all hydronically-heated structures.

摘要

全面了解循环加热结构的传热机制对于预测其加热性能至关重要。然而，很少有研究考虑加热管和主体材料界面处的传热。在本文中，对循环加热混凝土结构的两个关键界面（例如管道-混凝土界面和混凝土-空气界面）的传热进行了测试和分析。制造了两个混凝土块，一个带有嵌入式交联聚乙烯 (PEX) 管，另一个带有连接的 PEX 管，以代表用于传热研究的加热桥面板。这两个模块在冷冻箱内进行了一系列在不同室温和流体温度下的热响应测试。通过有限差分法 (FDM) 开发的方程，使用在不同深度测量的温度来计算混凝土和 PEX 管之间的对流传热系数和热接触导率。开发了两个块的有限元模型 (FEM)，以验证从一维热阻模型导出的热接触值。对模型的温度响应进行了全面分析，尤其是在两个界面处，FEM 模型能够准确预测实验室测量值。获得的接触传热系数和 FEM 模型可用于所有水力加热结构。开发了两个块的有限元模型 (FEM)，以验证从一维热阻模型导出的热接触值。对模型的温度响应进行了全面分析，尤其是在两个界面处，FEM 模型能够准确预测实验室测量值。获得的接触传热系数和 FEM 模型可用于所有水力加热结构。开发了两个块的有限元模型 (FEM)，以验证从一维热阻模型导出的热接触值。对模型的温度响应进行了全面分析，尤其是在两个界面处，FEM 模型能够准确预测实验室测量值。获得的接触传热系数和 FEM 模型可用于所有水力加热结构。