Phase-change heat-storage material (PCM) is widely used in many fields

and its thermophysical properties are the key factor for its application. In this study

an improvement of the T-history method is presented

based on the basic principle of the T-history curve method

the theoretical step curve of the PCM and the actual step-curve measurement process. Firstly

according to crystalline-melting thermodynamic conditions

a certain degree of supercooling is necessary for crystal crystallization; therefore

there is sensible heat between the phase-change-start phase and the phase-change-end phase. Then

the energy-balance equation was improved by considering the sensible heat effect on the energy-balance equation in the phase-change stage

and the temperature-difference effect on the energy-balance equation in the cooling process of the phase-transition phase. Secondly

the phase-change material was placed in a constant-temperature water source at 70 ℃ until it melted. Then

it was placed in a constant-temperature box at 10 ℃. The step curve was obtained with a two-second interval measurement. Finally

the experimental results for three phase-change materials

sodium dodecahydrate disodium phosphate

lauric acid

and stearic acid

were calculated according to the improved equations to verify the improvement of the T-history method. The results show that the calculated value of the latent heat is closer to that of the differential-scanning calorimetry process

and the error is less than 10%. Therefore

the improvement of the T-history method has a certain practical significance for the development and testing of phase-change thermal energy storage material.