Design of Heat Supply System Using Environmentally Benign Fluids Containing Supercritical Carbon Dioxide

本研究旨在利用二氧化碳（CO_2）与环境友好型溶剂碳酸二乙酯（DEC）在CO_2临界范围内混合产生的热量，开发环境友好型供热系统。在本研究中，为了完成供热系统，在之前科研资助项目设计的供热系统的基础上，尝试进一步研究流体循环系统。此外，还对CO_2偶联溶剂进行了寻找。本研究的细节和结果如下：1。在以前的系统中，只能在非常小的流量下运行。为此，对混合器进行了改进，旨在提高CO_2和DEC的流量，增强两者的混合效果。本研究主要考虑两种类型的混合器，即改进型单管混合器（混合器A）和多管混合器（混合器B）。总流速设定为0.2 mol/min。0.3 ~ 0.4 mol/min。分别为混合器A和B。从混合热回收的实验结果来看，当使用混合器A时，获得了最大回收热的最大值（约5.8 kJ/mol）。与我们之前测得的混合热最大值（9.0 kJ/mol）相比，混合热回收率最高可达70%左右。混合机A系统利用CO_2 + DEC系统的混合热作为供热系统。另一方面，混合器B的实验结果表明，增大管长可以提高混合效率。这些结果对混合器的改进有一定的参考价值。为了得到热效应较大的溶剂，本研究考虑到与CO_2的亲合力，选择了二异丙醚（DIPE）和甲基叔丁基醚（MTBE）两种醚作为溶剂。用等温微量热计（IMC）测定了CO_2 + DIPE和+ MTBE体系在298 ~ 308 K、5.0 ~ 7.5 MPa压力下的混合热。在298 K和5.0 MPa下，两种混合物的放热最大值均约为8.0 kJ/mol。该最大值略低于CO_2 + DEC体系。然而，这一热效应最大值比以往CO_2 +溶剂混合物的热效应最大值大1.6倍左右，可以认为它取得了积极的溶剂寻找结果。少

This study aims to develop the environmentally benign heat supply system using the heats of mixing of carbon dioxide (CO_2) and diethyl carbonate (DEC), which is environmentally benign solvent, in critical region of CO_2. In this study, for the completion of the heat supply system, further examinations concerning the cycle system of the fluids were attempted, on the basis of the heat supply system designed in the previous Grant-in-Aid for Scientific Research. In addition, a search of the solvent coupled with CO_2 was performed. Details and results of this study are as follows:1. In the previous system, it was possible to operate only in extremely small flow rate. Therefore, an improvement of the mixer was performed, aiming the increase of the flow rate of CO_2 and DEC, and the enhancement of mixing of them. In this study, two types of mixers, that is, an improved single-tube mixer (mixer A) and multi-tube mixer (mixer B) was mainly considered. Total flow rate was set to 0.2 mol/min., a … More nd 0.3-0.4 mol/min. for mixers A and B, respectively. From the experimental results of the recovery of the heats of mixing, when mixer A was applied, the largest value (about 5.8 kJ/mol) of the maximum recovered heats was obtained. The recovery ratio of the heats of mixing was maximum about 70 % compared with the maximum value of heats of mixing (about 9.0 kJ/mol) measured in our previous study. The system with mixer A is applicable as the heat supply system, by the use of the heats of mixing for CO_2 + DEC system. On the other hand, the results by mixer B indicate that the mixing efficiently will improve by making the tube length longer. These results would be useful for the improvement of the mixer.2. A search of the solvents coupled with CO_2 was performed by the measurements of the heats of mixing, in order to obtain the solvents accompanying larger heat effects, as well as DEC. In this study, two ethers, that is, diisopropyl ether (DIPE) and methyl tert-buthyl ether (MTBE), were applied as the solvents, considering the affinity with CO_2. The heats of mixing for CO_2 + DIPE and + MTBE systems were determined at temperatures 298-308 K, and pressures 5.0-7.5 MPa, using an isothermal microcalorimeter(IMC). Maximum value of exothermic was about 8.0 kJ/mol at 298 K and 5.0 MPa for both two mixtures. This maximum value was slightly lower than that of CO_2 + DEC system. However, this maximum value of heat effects is about 1.6 times larger than that of previous mixtures of CO_2 + solvent, and it is considered to achieve positive results of the search of solvents. Less