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

本研究的目的是利用二氧化碳（CO_2）与环境友好溶剂碳酸二乙酯（DEC）在临界CO_2浓度区的混合热，开发环境友好的供热系统。在本研究中，为了完成供热系统，在以前的科学研究补助金中设计的供热系统的基础上，尝试进一步检查流体循环系统。此外，还对CO_2与溶剂的耦合进行了探索。本研究的具体内容和结果如下：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。在这项研究中，两种类型的混合器，即改进的单管混合器（混合器A）和多管混合器（混合器B）主要考虑。总流速设定为0.2 mol/min，一 ...更多信息 对于混合器A和B分别为0.3-0.4 mol/min。从混合热的回收的实验结果，当应用混合器A时，获得最大回收热的最大值（约5.8kJ/mol）。混合热的回收率最大约为70%，与我们以前研究中测得的混合热最大值（约9.0 kJ/mol）相比。利用CO_2 + DEC系统的混合热，混合器A系统可作为供热系统。另一方面，混合器B的结果表明，通过使管长度更长，混合效率将得到提高。这些结果将有助于混频器的改进.通过混合热的测定，寻找与CO_2偶联的溶剂，以获得具有较大热效应和DEC的溶剂。考虑到与CO_2的亲合力，本研究选用了二异丙醚（DIPE）和甲基叔丁基醚（MTBE）作为溶剂。用等温微量热仪（IMC）测定了CO_2 + DIPE和+ MTBE体系在温度298-308 K、压力5.0- 7.5MPa下的混合热。两种混合物在298 K和5.0 MPa下的最大放热值均为8.0 kJ/mol。该最大值略低于CO_2 + DEC系统。然而，该热效应的最大值比先前的CO_2 +溶剂的混合物大约1.6倍，并且被认为在溶剂的搜索方面取得了积极的结果。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