Abstract: In order to measure the isobaric specific heat capacity([cp])of hydrocarbon fuels at high temperature and high pressure conditions accurately，a new experimental method and device were developed based on the relation between[cp]and enthalpy. The influence of heat loss on the measurement accuracy can be reduced significantly based on this method. The relative uncertainty of the method for isobaric heat capacity measurements is 3.7% in the temperature range of 300K to 800K according to the uncertainty analysis. Validation experiments were conducted by measuring the[cp]of n-decane(3MPa and 5MPa，312～797K). The test results indicate that the average absolute deviation(AAD)is below 1.8%，and the maximum absolute deviation(MAD)is 4.3%，excluding the pseudo-critical region where the MAD is 7.6% due to sharp variations of isobaric heat capacity. Test results are tabulated in the temperature range of 675K to 797K on 3MPa and 5MPa，which extended the data range of existing data. This method can be also applied to other fluids in similar operating conditions.

Key words: Isobaric specific heat capacity；Measurement; n-decane；Thermophysical properties；Super-critical

摘要： 为了准确测量高温高压条件下燃油的定压比热，基于定压比热与焓值的关系，提出一种适用于测量高温高压流体定压比热的方法并设计相应的实验装置，该方法可以显著地减小热损失测量误差对测量结果的影响，提高比热测量精度。经过误差分析，在常温至800K范围内，该方法具有最大3.7%的相对不确定度。利用该方法对正癸烷的定压比热(3MPa和5MPa，312～797K)进行了标定实验，实验结果表明，定压比热测量的平均偏差小于1.8%，拟临界点附近最大偏差7.6%，其它温度范围最大偏差不超过4.3%。对3MPa和5MPa下675～797K的正癸烷定压比热数据进行了补充。该方法同样适用于其它流体在该温度范围内的定压比热测量。

关键词: 定压比热；测量；正癸烷；热物性；超临界