Effects of Ambient Condition on the Performance of Ammonia Based Loop Heat Pipe

The loop heat pipe (LHP) is a two-phase heat transfer device used for thermal management in different applications like spacecraft, mobile, laptop, electronic cooling etc. Ambient condition has significant effect on the performance of LHP. In the present work, modeling of LHP with ammonia as a working fluid was done in MATLAB with two-phase analysis and effects of ambient conditions (i.e., 5 °C, 19 °C and 25 °C) on the parameters like i.e., steady state operating temperature (SSOT), condenser outlet temperature (Tco), liquid line outlet temperature (Tlo), pressure drop across liquid line, vapor line, wick, condenser (i.e., $$\Delta P_{{l{\varvec{l}}}} , \Delta P_{{v{\varvec{l}}}} , \Delta P_{w} , \Delta P_{{2\upphi }}$$ ), heat exchange from compensation chamber (C.C.) and liquid line to ambient (i.e., Qc.c.-amb, Qll-amb) were analyzed. When Tamb was increased from 5 to 25 °C SSOT, Tco and Tlo increased by 4.59 °C, 4.06 °C and 5.35 °C respectively at 600 W. Heat transfer from the liquid line to the ambient caused Tco to be greater than Tlo at lower ambient temperature whereas Tlo was found to be higher than Tco at higher ambient temperatures due to heat transfer from the ambient to the liquid line. $$\Delta P_{{2\upphi }}$$ and $$\Delta P_{w}$$ both have significant effect on ΔPtotal at higher heat loads whereas at lower heat loads $$\Delta P_{w}$$ was found to be dominant. Qc.c.-amb and Qll-amb were observed to be deceasing with increase in Tamb from 5 to 25 °C.