Condensation heat transfer and pressure drop data of R-134a in annular helical pipes is of significant importance to the effective design and reliable operation of helical pipe heat exchangers for refrigeration, airconditioning, and many other applications. This paper presents the experimental investigation on condensation heat transfer and pressure drop characteristics of R-134a in an annular helical pipe. The average condensation heat transfer coefficients and pressure drops were experimentally determined for R-134a at three different saturated temperatures (35 8C, 40 8C, and 46 8C). The experimental results are compared with the data available in the literature for helical and straight pipes.

A total energy system (TES) incorporating a solid oxide fuel cell (SOFC) and an exhaust gas driven absorption chiller (AC) is presented to provide power, cooling and/or heating simultaneously. The purpose for using the absorption chiller is to recover the exhaust heat from the SOFC exhaust gas for enhancing the energy utilization efficiency of the TES. A steady-state mathematical model is developed to simulate the effects of different operating conditions of SOFC, such as the fuel utilization factor and average current density, on the performance of the TES by using the MATLAB softpackage. Pametric analysis shows that both electrical efficiency and total efficiency of the TES have maximum values with variation of the fuel utilization factor; while the cooling efficiency increases, the electrical efficiency and total efficiency decrease with increase in the current density of SOFC. The simulated results could provide useful knowledge for the design and optimization of the proposed total energy system.

This paper presents an experimental investigation of condensation heat transfer of alternative refrigerant R-134a flowing inside a helical pipe with cooling water through the concentric annular passage in a counter-flow direction. The experiments were conducted with the helix axis of the test section in horizontal, vertical, and inclined orientation directions, respectively. The mass flow flux for R-134a ranges from 100 to 400kg/m2s and the Reynolds number of cooling water ranges from 1500 to 10000. The results demonstrate the orientation of helical pipe has a significant effect on both refrigerant-side heat transfer and overall heat transfer coefficients.

A total energy system (TES) incorporating a solid oxide fuel cell (SOFC) and an exhaust gas driven absorption chiller (AC) is presented to provide power, cooling and/or heating simultaneously. The purpose for using the absorption chiller is to recover the exhaust heat from the SOFC exhaust gas for enhancing the energy utilization efficiency of the TES. A steady-state mathematical model is developed to simulate the effects of different operating conditions of SOFC, such as the fuel utilization factor and average current density, on the performance of the TES by using the MATLAB softpackage. Parametric analysis shows that both electrical efficiency and total efficiency of the TES have maximum values with variation of the fuel utilization factor; while the cooling efficiency increases, the electrical efficiency and total efficiency decrease with increase in the current density of SOFC. The simulated results could provide useful knowledge for the design and optimization of the proposed total energy system.

利用燃料电池的经验方程建立了质子交换膜燃料电池（PENFC）的一雏稳态模型，进行了仿真和结果分析，仿真结果与实验数据吻合较好利用VB（Visual Basic）编写人机交互界面作为前台用户程序，以MATLAB的SIMULINK在后台运行，发展了一种基于MATLAB和vB软件包的质子交换膜燃料电池特性参数仿真实验软件，并对PEMFE的工作温度、反应气压力等参数对其性能的影响进行了仿真分析，有助于进行燃料电池特性参数仿真实验以及对燃料电池的分析、设计和优化。