热容的计算

论述各种情况下气体、液体和固体热容的计算方法。     

一种比定容热容测量装置

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%。     

CO2-烃类液相混合物比定容热容的实验与模型研究

近年来,二氧化碳(CO₂)提高原油采收率(CO₂-EOR)技术得到了广泛的研究。充分了解CO₂-烃类混合物的热容性质是该项目能够成功实施的基础,但是目前对此性质的研究非常有限。基于绝热量热法,搭建了一个绝热量热计,测量了温度为317.15~353.15 K,压力高达29.49 MPa时,CO₂-碳氢化合物(正己烷、正辛烷、十一烷、环己烷、乙苯)二元液相混合物的比定容热容(C_v )数据,共获得335个数据点。此外,采用预测模型(结合热力学关系的PR状态方程)和经验模型计算C_v,计算平均绝对相对偏差(AARD)分别为0.81%~3.66%和小于2.56%。经验模型的形式简单,但PR模型有较强的预测能力。实验测得的C_v 数据以及建立的两种计算模型对CO₂-EOR项目的实施至关重要。     

溴氰菊酯低温热容的测定及热化学性质

采用精密自动绝热量热计测量了溴氰菊酯在80～400 K温区的热容,试样纯度为0.9926（摩尔分数）.在此温区内出现一个固-液熔化相变,其熔化温度T_m、摩尔熔化焓Δ_fusH_m、摩尔熔化熵Δ_fusS_m分别为（372.15±0.02）K,（26.73±0.02）kJ·mol^-1,（71.81±0.06）J·K^-1·mol^-1.报道了该物质在298.15～400 K温区内每隔5 K的热力学函数H_(T)-H_(298.15),S_(T)-S_(298.15),G_(T)-G_(298.15)值.采用DSC法对试样进行了测定,并与绝热量热法进行了比较.用热重法研究了该化合物的热分解行为,得到分解反应动力学参数反应级数n、频率因子A及活化能E分别为1.78,1.15×10⁹min^-1,603.8 kJ·mol^-1.     

气体分子平均热容的温度函数

在硫酸工艺设计计算中,经常用到SO_3、SO_2、O_2、N_2、空气、NO、H_2O、H_2S等气体分子的平均热容。但在现有资料中,可供查阅的气体分子平均热容数据十分有限。例如文献[1]中提供的气体分子平均热容,只有温度为100℃的整数倍时的数据,当温度不是100℃的整数倍时,虽有相应的气体分子平均热容曲线可查,但因图形太小,查出的热容数据误差较大,且查图十分麻烦。另一方面,在电子计算机广泛应用于化工领域的今天,计算机辅助化工工艺设计巳得到应用,对此来说,使用图表式的数据是十分不便的(因为频繁地输入数据,浪费     

功率振荡式反应釜传热因子和系统热容测量

针对夹套式反应釜传热因子UA和系统热容cpm测量效率低的问题,提出一种功率振荡式校正方法。测量过程中夹套油温固定,控制校正加热器输出振荡功率使样品温度产生反向对称的两周期升降,利用过程中多次等效测量平均值获取传热因子和系统热容。以去离子水和二丙二醇为样品设计实验,验证该方法在不同温度、液位条件下的有效性,并与2种方法的测量结果进行对比。结果表明,功率振荡校正方法的测量精度与现有方法基本相当,但具有更高的测量效率。     

1,2-环己二醇标准摩尔燃烧焓和定压热容测定

采用GR-3500型氧弹量热计实验测定了顺式-1,2-环己二醇和反式-1,2-环己二醇的标准燃烧焓,分别为-3507.043kJ/mol和-3497.8kJ/mol,并用萘作标准物验证测试仪器,其实验测定值与文献值相对误差为0.053%,同时推算出环己二醇的标准摩尔生成热,分别为568.997kJ/mol(顺式)和578.240kJ/mol(反式)。用NETZSCHDSC204型差示扫描量热仪测定了1,2-环己二醇的定压热容,拟合出环己二醇摩尔定压热容与温度之间的函数关系;同时还测定了1,2-环己二醇的熔点和熔化热,为该产品的新工艺开发、工程设计和工业化生产提供了基础数据。     

气体分子平均热容的温度函数

该文应用文献中提供的热容数据,编制出回归软件包进行拟合,得出了常压下十几种常用气体分子平均热容的温度函数计算公式,其形式、计算值与丈献形式、文献值一致。可供从事化工工艺设计的人员直接使用。     

管壳式混合蒸气冷凝器换热面积的校核计算

通过数学模型描述了冷凝过程的传热与传质机理;并利用简便设计法原理分过热段和饱和段对管壳式混合蒸气冷凝器进行了换热面积的校核计算。由计算实例对其计算精度和有效性做了验证,同时指出了换热面积随冷凝过程的变化规律。     

Calculation of Vapor‐Liquid Equilibrium Data of Binary Mixtures Using Vapor Pressure Data

The design of plants or unit operations requires the knowledge of data for multicomponent systems. An approach is presented for the regression of binary interaction parameters required for the calculation of activity coefficients. Binary vapor pressure data are used to correlate these parameters for calculation of vapour/liquid equilibrium data. The advantage of the approach is the fact that only easily measured vapor pressure data are required. The procedure is demonstrated by means of two binary mixtures. Parameter regression, prediction of vapour/liquid equilibrium data as well as their experimental verification are demonstrated.     

Vapor Condensation Heat Transfer in a Thermoplate Heat Exchanger

The heat transfer and pressure drop in a thermoplate heat exchanger operating as a condenser have been investigated experimentally. In order to separate the heat transfer resistances in the condensation process, the single phase forced convection has been studied using distilled water and Marlotherm oil in the thermoplate and correlations developed for the Nusselt number and the friction factor. For the condensation experiments, an apparatus has been constructed comprising two identical condensers composed of the same thermoplate type as employed in the single phase experiments. Isopropanol is used as a test fluid at pressures below atmospheric pressure. The heat transfer resistances in the condensation experiments are separated and expressions for the condensation heat transfer and pressure drop are developed with the aid of the results obtained in the single phase studies.     

Heat capacity of rocket propellant (RP-1 fuel) at high temperatures and high pressures

Isobaric heat capacity of rocket propellant (RP-1 fuel) has been measured with a vacuum adiabatic calorimeter immersed in a precision liquid thermostat. Measurements were made in the temperature range from 293 to 671 K and at pressures up to 60 MPa. The uncertainty of heat capacity, pressure, and temperature measurements were estimated to be 2-2.5%, 0.05%, and 15 mK, respectively. The measured values of heat capacity were compared with the values calculated from a surrogate mixture model (equation of state, EOS). The average absolute deviation (AAD) between the present data and the values calculated with EOS was 0.81%.     

用纯组分蒸汽压方程关联汽液平衡

将经典热力学关系式与双流体模型相结合，由纯物质的蒸汽压方程关联了卤代烷烃和卤代烯烃体系的二元汽液平衡，只需要一个二元相互作用参数，其计算精度相当于或略优于二参数的Ｗｉｌｓｏｎ方程。     

恒温式氧弹热量计热容量的标定

采用同一标定过程,同时采集符合GB/T213—2003和GB384—1981中标定恒温氧弹热量计热容量所需的数据,然后采用各自陈述的方法计算。在不同室温下得到的热容量值,除有不具随机特性的负偏差外,还随室温变化;尤其温差较大时,差值具有显著性。认为用热量计测定物质热值时,要用同一方法测量和计算,且环境温度应尽可能接近。     

六氟丙烯的蒸汽压

六氟丙烯的蒸汽压李昌圣冯耀声吴兆立（浙江大学化工系，杭州３１００２７）关键词蒸汽压六氟丙烯１前言六氟丙烯是氟利昂２２裂解制四氟乙烯过程中的主要副产物，而且四氟乙烯和六氟丙烯的共聚物（ＴｅｆｌｏｎＦＥＰ）和聚四氟乙烯一样是性能优良的工程塑料，具有卓越...     

乙酸—丙酸二元系气相PVTx关系

本文测定了乙酸、丙酸及其混合物在70～110℃和4～67 kPa范围内的气相PVTx数据,并用二缔模型处理,得到了乙酸、丙酸及其混合物的二缔平衡常数和缔合焓的实验值。这些缔合常数可用于汽液平衡计算。     

Identification of Physical Phenomena Governing Nucleate Boiling Heat Transfer of Binary Mixtures

A model based on first principles is presented to compute nucleate boiling heat transfer coefficients. It includes microscale heat and mass transfer phenomena in the so‐called micro region, i.e., the thin film area where the liquid vapor phase interface approaches the wall. The model is verified by comparing calculated to measured heat transfer coefficients. Parameter studies allowed to identify physical phenomena governing the typical reduction of binary mixture heat transfer coefficients compared to the ideal heat transfer coefficient, i.e., the molar average of the heat transfer coefficients of the two pure components of the mixture. These are bubble site density and departure diameter that deviate from the corresponding values of the two pure components. Furthermore, overall heat transfer is decreased by strong concentration gradients in the micro region.