Experimental Comparison of Mobile A/C Systems When Operated With Transcritical CO2 Versus Conventional R134A
Experimental Comparison of Mobile A/C Systems When Operated With Transcritical CO2 Versus Conventional R134A
复制标题
DOI：
--
复制
发表时间：
1998
期刊：
影响因子：
--
通讯作者：
R. Mcenaney;D. E. Boewe;J. Yin;Y. Park;C. Bullard;P. Hrnjak
中科院分区：
文献类型：
--
作者：
R. Mcenaney;D. E. Boewe;J. Yin;Y. Park;C. Bullard;P. Hrnjak
本文介绍了汽车跨临界co2系统的原型与对应的Rl34a系统的性能对比实验，该系统被选为美国、欧洲和日本市场的代表。本文介绍了进行这种比较和初步结果的实验设计和设备。本项目的一个目标是为TEWI （Total Equivalent Warming Impactsee Sand at al. 1997）的计算提供一个实验验证的基础，特别是对于像Pettersen et al. （1997a）和（1997b）这样非常稀疏的R744。还定义了测试矩阵，用于开发组件和系统仿真模型，以及在正常、季节性和极端操作条件下支持数据对数据的比较。由于无法获得成本数据，Rl34a和co2系统的比较是基于相同的热交换器芯体积。组件体积被限制为相等；由于设计中使用了相同的材料，因此假设重量相似。面部面积保持相等。更多细节见表1。空气体积流量和空气侧压降基本保持不变，见表2。每个热交换器都建造了单独的环境室，每个环境室都包含风洞，并为两种制冷剂提供单独的管道。每个热交换器获得三个能量平衡：空气侧，制冷剂侧和室内量热。特别注意开发测试设施，以在广泛的工作范围内产生准确的数据，主要是在稳态下，也在瞬态（主要是循环）条件下。采用三种独立的方法，而不是所有适用标准所要求的两种方法，这不仅有利于系统容量的确定，而且当制冷剂量热法由于两相出口而不可靠时，也可以采用两种方法。这主要发生在瞬态，并与恒定面积膨胀装置。三个独立的程序也提高了我们排除早期测试故障的能力。测试设备由两个环境室组成（见图1），可保持室内外温度在±0.5℃，绝对湿度在±2%。每个腔室的变速风洞模拟了实际应用中遇到的操作条件范围，并允许测量±1%的空气流速。科里奥利质量流量计，连同每个组件的上游和下游的浸入式热电偶和电子压力传感器，可产生在±1%内重复的制冷剂侧容量测定。房间量热法是最精确的：墙壁由30厘米厚的聚氨酯制成。每个环境室的墙壁、地板和天花板两侧各有5个热电偶。传输损耗经过仔细校准，使误差在±0以内。1%，所有干能量输入（电）测量在±0.2%范围内。特别注意确保热交换器入口温度和速度分布的均匀性，以及出口空气温度和湿度的代表性读数。测试结果表明，独立确定的容量之间的一致性在±5%以内，主要是由于空气侧量热法的不确定性。图2和图3显示了空气和制冷剂侧以及环境室的热平衡差异。
This paper describes the experimental comparison of performance of prototype transcritical C02 system for mobile ale to it's Rl34a counterpart, unit for Ford Escort that was chosen as a representative for the US, European, and Japanese markets. The paper presents the design of experiments and facilities for such comparisons and preliminary results. INTRODUCTION One objective of this project is to provide an experimentally verified basis for calculation of TEWI (Total Equivalent Warming Impactsee Sand at al. 1997), particularly for R744 that are very sparse like Pettersen et al. (1997a) and (1997b). Test matrices are also defined for the purpose of developing component and system simulation models, as well as supporting data-to-data comparisons at normal, seasonal and extreme operating conditions. The comparison of Rl34a and C02 system is based on equal heat exchanger core volumes because cost data were unavailable. Component volumes were constrained to be equal; the weight was assumed be similar due to same materials used for the design. The face areas are kept equal. More details could be found in Table 1. Volumetric flow rates of air and air side pressure drops are maintained almost the same and are shown in Table 2. EXPERIMENTAL FACILITIES Separate environmental chambers have been constructed for each heat exchanger, each containing wind tunnel with separate piping for the two refrigerants. Three energy balances are obtained for each heat exchanger: air-side, refrigerant-side and room calorimetry. Special care was taken to develop test facilities that will produce accurate data in wide operating ranges, primarily in steady-state but also in transient (mostly cycling) conditions. Three independent methods are used instead of the two required by all applicable standards, not only to facilitate determincrtion of system capacities, but also to have two whenever refrigerant calorimetry is not reliable due to two-phase exit. This occurs mostly during transients, and with constant area expansion devices. Three independent procedures also improved our ability to troubleshoot early tests. The test facility consists of two environmental chambers (see Figure 1) that can maintain outdoor and indoor temperature within ±0.5°C and absolute humidity ±2%. A variable speed wind tunnel in each chamber simulates the range of operating conditions encountered in real applications, and allows measurement of air-flow rates within ±I%. Coriolis mass flow meters, together with immersion thermocouples and electronic pressure transducers upstream and downstream of every component yield refrigerant-side capacity determinations repeatable within ±I%. Room calorimetry is the most accurate: the walls are made of 30cm thick polyurethane. There are five thermocouples on both sides of each wall, floor, and ceiling of each environmental chamber. Transmission losses are carefully calibrated so that error is within ±0 .1 %, all dry energy inputs (electric) are measured within ±0 .2%. Special care is taken to ensure uniformity of the temperature and velocity profiles at the inlet to the heat exchangers, and representcrtive reading of the exit air temperatures and humidities. Test results show agreement between the independently determined capacities to be within ±5%, primarily due to uncertainties in air-side calorimetry. Figures 2 and 3 show the differences in heat balances determined on air and refrigerant side and for the environmental chamber.