Heat Transfer Case Study

8.1.5 heat transfer in nucleation boiling

In the heat transfer, the 3 temperature is needed. It is wall temperature, Tw, saturation temperature, Tsat, liquid temperature, TL. To determine the heat transferred coefficient, the wall temperature must minus to the saturation temperature (Tw - Tsat). The heat transfer is interrelated driving temperature contrast, refer equation [15 – 20] below [40]. q^''=c_1 〖(T_w- T_sat)〗^m {15} q^''=h(T_w- T_sat) {16} h= c_2 〖(T_w- T_sat)〗^(m-1) = c_2 〖(T_w- T_sat)〗^n {17} h= c_3 〖q''〗^((m-1)/m)= c_3 〖q''〗^P {18}

For case study of evaporation:- h= c_2 〖(T_w- T_sat)〗^(1⁄4) {19} Laminar flow h= c_2 〖(T_w- T_sat)〗^(1⁄3) {20} Turbulent flow

The value of “m”, “n”, and “P” from table below:-

Table 1.0: Comparison between

Heat transfer will be happen in two condition, it is evaporation and pool boiling nucleation. In the evaporation condition, there is 2 type of flow, it is fast flow or turbulent flow and slow flow or laminar flow. 3 type of heat transfer is happened during nucleate the bubble. First the conduction heat transfer from heater surface to working fluid, second convection heat transfer from just a little above heated surface to working fluid (natural convection) and third is evaporation from the micro layer of the bottom of vapor bubble and top surface of working fluid, bubble release to the atmosphere pressure [40]. Working fluids

8.2.1 Base fluids

HFE7000 is one of the trendy use for research purpose of refrigerant type, even this year still have researcher doing research use this type of refrigerant. The earliest HFE7000 use as working fluid in experimental research in 2012 [41]. The main properties of this refrigerant is shown Table 2.0.

Table 2.0: Properties of HFE7000 [42].

Properties Value

Molecular Weight (g/mol) 200

Boiling Point @ 1 atmosphere (°C) 34

Freeze Point (°C) -122.5

Liquid Density (kg/m3)