一种比定容热容测量装置

doi:10.11949/0438-1157.20190501

摘要/Abstract

摘要：

比定容热容是基础状态方程建立和工程计算的基础热数据。基于绝热量热法研制了一种比定容热容测量装置，使用混合工质节流制冷机实现大温跨制冷并提供稳定的冷量；通过设置双层被动式控温防辐射屏并自主设计PID控温程序，在整个测量过程中样品容器与防辐射内屏的温差小于0.2 K，有效减小了辐射漏热；温度计内置于样品容器，减小了温度梯度，测温更加准确。通过测量异丁烷在279.10～323.68 K温区的压缩液体比定容热容对实验装置的可靠性进行验证。异丁烷的实验数据与文献数据具有较好的一致性，且与REFPROP 9.1的计算值对比最大绝对偏差为1.63%，平均绝对偏差为0.88%。

关键词: 比定容热容, 热力学性质, 绝热量热计, 辐射, 异丁烷, 压缩液体, 状态方程

Abstract:

As one of the most important thermodynamic properties, isochoric specific heat capacity is related to the calculation of internal energy and entropy, is the key parameter of engineering design. What is more, isochoric specific heat capacity is derived by the second derivative of pressure with respect to temperature and is important for verifying the accuracy of equation of state. An adiabatic calorimeter was developed to measure the isochoric specific heat capacity. A spherical bomb with platinum resistance thermometer inserted was used to hold the measured liquid. The cooling capacity was provided by a mixed-refrigerant Joule-Thomson refrigerator. In view of the difficult problem of heat insulation in a wide temperature range, two adiabatic shields were arranged and the PID temperature control method was designed independently to reduce the temperature difference between the bomb and the adiabatic shield. The temperature difference between the bomb and the inner adiabatic shield was less than 0.2 K throughout the experiment. In order to verify the reliability of the experimental setup, the isochoric specific heat capacity data of isobutane were measured over temperatures from 279.10 K to 323.68 K. Satisfactory agreement with published heat capacity data is found and the average absolute relative deviation between this data and the values calculated from REFPROP 9.1 is 0.88%.

Key words: isochoric specific heat capacity, thermodynamic property, adiabatic calorimeter, radiation, isobutane, compressed liquid, equation of state

中图分类号:

TK 123

钟权, 董学强, 赵延兴, 王敬洲, 张海洋, 沈俊, 公茂琼. 一种比定容热容测量装置[J]. 化工学报, 2019, 70(S2): 20-24.

Quan ZHONG, Xueqiang DONG, Yanxing ZHAO, Jingzhou WANG, Haiyang ZHANG, Jun SHEN, Maoqiong GONG. Apparatus for isochoric specific heat capacity measurement[J]. CIESC Journal, 2019, 70(S2): 20-24.

图/表 5

图1 绝热量热实验装置结构1—制冷机；2—天平；3—配气瓶；4~6—真空泵；7—直流电源；8—keithley2002数据采集表；9—压力传感器；10—计算机；11—绝热外屏；12—绝热内屏；13—样品容器；14—Pt25温度计

Fig.1 Schematic diagram of adiabatic calorimeter

图2 样品容器

Fig.2 Sample container

表1 异丁烷的详细信息和常用物性

Table 1 Detailed information and common properties for isobutane

物质

CAS

登记号

摩尔

纯度

T_c^①/K

表2 异丁烷液体比定容热容实验数据

Table 2 Values measured for isochoric specific heat capacity of compressed liquid isobutane

T/K	p/MPa	ρ^①/（kg·m^-3）	c_v/(kJ·kg^-1·K^-1)	u_r(c_v)/%
279.10	1.279	575.48	1.596	1.22
281.30	2.694	575.23	1.606	1.20
283.53	4.114	574.97	1.617	1.20
285.76	5.533	574.72	1.625	1.20
288.00	6.958	574.48	1.639	1.19
290.24	8.378	574.25	1.651	1.18
292.49	9.794	574.01	1.652	1.18
294.73	11.195	573.77	1.670	1.19
296.93	12.568	573.54	1.683	1.19
302.54	1.141	546.76	1.718	1.18
304.80	2.338	546.53	1.727	1.16
307.09	3.552	546.30	1.736	1.15
309.44	4.791	546.07	1.753	1.12
311.82	6.038	545.83	1.749	1.13
314.15	7.258	545.60	1.771	1.13
316.53	8.495	545.37	1.774	1.10
318.93	9.734	545.12	1.799	1.12
321.28	10.942	544.88	1.814	1.12
323.68	12.165	544.63	1.819	1.09

图3 异丁烷液相cv实验结果与REFPROP 9.1计算值偏差

Fig.3 Relative deviations between measured cv of isobutane and values calculated from REFPROP 9.1

参考文献 17

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