Nonlinear fitting method for cooling process of polymeric phase change material

Abstract

The present invention discloses a nonlinear fitting method for a cooling process of a polymeric phase change material. The method comprises the following steps of: (1) taking the polymeric phase change material as a to-be-tested sample, heating the to-be-tested sample to an initial temperature T1, holding the temperature until the to-be-tested sample is completely melted, then rapidly transferring the to-be-tested sample into a cooling medium of which the temperature is T2, inserting a T-shaped thermocouple into the melted to-be-tested sample at the same time, and acquiring temperature variation values of the to-be-tested sample in the whole cooling process; (2) according to temperature and time data acquired in the step (1), drawing a cooling curve; (3) performing dimensionless processing on the cooling curve, and setting a dimensionless temperature theta to be equal to the value of (T-T2) / (T1-T2); and (4) according to the theta value obtained in the step (3), performing nonlinear fitting by means of the following algorithm: y=(A+B) / (C+ex-D)-B, and making x equal to ln t and y equal to theta, so that a nonlinear fitting parameter in the cooling process of the polymeric phase change material can be obtained. A four-parameter model formula fitting method proposed by the present invention is convenient, has very good fitting effects for different polymeric phase change materials, and is higher in fitting accuracy.

Description

technical field [0001] The invention belongs to the field of polymer phase-change materials, and in particular relates to a nonlinear fitting method for the cooling process of polymer phase-change materials. technical background [0002] Phase change energy storage material (PCM) refers to a class of substances that can automatically absorb or release latent heat from the environment by using the phase state or structure change of the material itself within a certain temperature range, thereby achieving the regulation of the ambient temperature. The specific phase transition process is: when the ambient temperature is higher than the phase transition temperature, the material absorbs and stores heat to lower the ambient temperature; when the ambient temperature is lower than the phase transition temperature, the material releases the stored heat to increase the ambient temperature. For example, in winter, phase change energy storage materials can absorb solar energy during t...

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Problems solved by technology

However, after research, it is found that although the three-parameter model has a good fitting effect in the cooling process of the phase change material as a whole, there is still a large deviation between the initial cooling stage and the measured temperature value. Based on this, the present invention proposes A "four-parameter" equation was established, and the nonlinear fitting results of the curves showed that this method has better fitting effects in the cooling process of different polymer phase change materials.

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