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ABSTRACT
An experimental investigation on condensation heat transfer of R290 with inside diameter of 6.3 mm in horizontal micro-fin tube was presented. Effects of each case on the condensation heat transfer coefficient of R290 were analyzed at saturation temperatures of 40°C, 50°C, and 55°C with heat flux ranging of 3–8 kW/m2, mass flux ranging of 100–250 kg/(m2·s) and vapor quality up to 1.0. The results show that the condensation heat transfer coefficients increase with mass flux and heat flux, however decrease with saturation temperature. In addition, compared with the smooth tube, the condensation heat transfer coefficients of R290 in the micro-fin tube increase by about 25%. Comparing the experimental data, the condensation heat transfer correlations of Yu et al. has high accuracy.
Nomenclature
| = | specific heat capacity at constant pressure [J/(kg·°C)] | |
| d | = | inside diameter [mm] |
| D | = | outside diameter [mm] |
| e | = | mean deviation [%] |
| G | = | mass flux [kg/(m2·s)] |
| = | heat transfer coefficient [W/(m2·°C)] | |
| Hf | = | tooth head [mm] |
| = | specific enthalpy [J/kg] | |
| = | latent heat [J/kg] | |
| I | = | electric voltage [A] |
| = | tube length [mm] | |
| m | = | mass flow [kg/s] |
| n | = | thread number |
| N | = | point number |
| p | = | pressure [MPa] |
| P | = | heating power [W] |
| q | = | heat flux [kW/m2] |
| Q | = | heat transfer rate [W] |
| R | = | single error |
| t | = | temperature [°C] |
| T | = | temperature [°C] |
| u | = | velocity [m/s] |
| U | = | electric voltage [V] |
| V | = | volume flow [L/min] |
| = | vapor quality | |
| = | influencing factor |
Greek symbols
| α | = | addendum angle [°] |
| β | = | thread angle (°) |
| = | ratio | |
| δ | = | total wall thickness [mm] |
| δw | = | bottom wall thickness [mm] |
| = | systematic error | |
| = | value of the factor | |
| = | thermal conductivity [W/(m2·°C)] | |
| = | density [kg/m3] | |
| = | temperature difference [°C] | |
| = | vapor quality decrement |
Subscripts
| A | = | absolute relative |
| cw | = | cooling water |
| exp | = | experimental |
| i | = | inside |
| in | = | inlet |
| L | = | liquid |
| m | = | mean |
| o | = | outside |
| out | = | outlet |
| pre | = | predicted value |
| preh | = | preheating section |
| ref | = | refrigerant |
| R | = | relative |
| sat | = | saturation |
| v | = | vapor |
| w | = | wall |