A latent heat model of vaporisation of water with critical temperature

The model uses an equation for a general expression of the latent heat of vaporisation of water in the vicinity of and far away from the critical temperature, which was presented by Torquato and Stell 1982.

Denoting the critical temperature as T_c, and introducing a dimensionless variable \tau=(T_c-T)/T_c associated with temperature T, the equation is given by

    L(\tau) = a_1 \tau^{\beta}+a_2 \tau^{\beta+\Delta}
              +a_4 \tau^{1-\alpha+\beta}
             +\sum_{n=1}^{M}(b_n \tau^n),\,\text{[kJ/kg]},

where the parameters of b_n are obtained by the least square method by fitting the equation with the experiment data.

In this model, the parameter set of M=5 is taken for a high accuracy. The parameters are given below:

• \alpha=1/8,\,\beta=1/3,\, \Delta=0.79-\beta,
• a_1=1989.41582,\, a_2=11178.45586, a_4=26923.68994,
• b_n:=\{-28989.28947, -19797.03646, 28403.32283, -30382.306422, 15210.380\}.

The critical temperature is 373.92 ^{\circ}C.

A comparison of this model with the model of is given in the following figure:

Based on the comparison, a conclusion can be drawn such that the linear model can be applied for the applications with temperature below 400 K.

(The above context is from the documentation of the presented class in this MR.)

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