Abstract
Pulsating heat pipe’s (PHP) are one of the alternatives to conventional heat transfer technologies. First part of this paper, titled: thermohydrodynamic behavior of methanol charged closed loop pulsating heat pipe has given information about thermo-hydrodynamic operational characteristics such as; bubble nucleation and collapse, bubble agglomeration and pumping action, flow regime changes, pressure/temperature perturbations, dynamic instabilities, meta-stable non-equilibrium conditions etc. in the PHP. Present paper, which is an extension of the previous work, it presents some more thermal results to highlight the effect of; thermo-physical properties of working fluid, filling ratio and number of turns on thermal performance of PHP. Three different PHP loop has been made from six, four and two parallel glass tubes (i.e. three turns, two turns and one turn at evaporator section) forming adiabatic section, interconnected alternately by copper U tubes, having internal and external diameter 2 mm and 3.06 mm respectively. The length of evaporator, condenser and adiabatic section are 42 mm, 50 mm and 170 mm respectively. The experimentation conducted for different working fluids (water, ethanol, methanol and acetone), different filling ratio’s (30%FR, 50%FR and 70%FR) and different number of turns (one, two and three turns). The motto of present research is to understand the thermal performance in terms of thermal resistance of PHP in details. The result shows that, thermal resistance for all working fluid PHP’s rapidly decreases with increasing heating power up to 32W. For low heating power, working fluid (acetone) which has lower boiling temperature is best, but it cannot give the service for higher heating power. Two turn PHP loop with methanol 50% volumetric filling ratio at more than 32W heating power with one directional flow circulation is the optimum operating condition of present research.
Highlights
Closed Loop Pulsating Heat Pipe (PHP) is a two-phase passive heat transfer device proposed and patented by Akachi (1990)
The steady-state has reached for each heat input level temperature for different points recorded and the overall thermal performance of the PHP has been estimated
Effect of different working fluids:From the above description it is concluded that, the fluid which has lower boiling point is more suitable for lower heating power because of sufficient evaporation rate but the situation is reversed in case of high heating power
Summary
Closed Loop Pulsating Heat Pipe (PHP) is a two-phase passive heat transfer device proposed and patented by Akachi (1990). A PHP is a simple in structure with a small diameter coil partially filled with certain working fluid in it and extended from the heat source to sink. PHP uses the technique of transporting the working fluid by means of differential pressure across liquid slugs and vapor plugs from evaporator to condenser and reverse. The fluid from the evaporator is pushed towards the condenser in the form of discrete liquid slugs and vapor bubbles. A PHP is being explored for thermal management of electronic devices to remove heat without any electrical power supply and it able to dissipate substantial amount of heat with small temperature drop, simple design and low cost
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