The Helical Oscillating Heat Pipe: Flow Pattern Behaviour Study

Abstract

This research aims to study the effect of evaporator temperature, pitch distance, and working fluid on the internal flow pattern and the heat transfer characteristics of the helical oscillating heat pipe. A Pyrex tube with an inner diameter of 2.4 mm was used to study the flow pattern in the evaporator section. The pitch distance varied at 1, 1.5, and 2 cm. Water and R-123 were used as working fluid with a filling ratio of 80% by total volume. In the evaporator section, the water temperature varied at 60, 75, and 90 ∘ C to supply heat to the heat pipe. In the condenser section, air with a temperature of 25 ∘ C was used as heat sink. From the results, it was found that 4 internal flow patterns, bubble flow, slug flow, annular flow, and stratified wavy flow, were observed in the evaporator section for both working fluids. The heat transfer rate decreased when the pitch distance was increased from 1 to 2 cm. The maximum heat flux was 2,132.6 and 1,773.4 W/m 2 for the working fluid of R-123 and water, respectively. Both occurred at a pitch distance of 1 cm and an evaporator temperature of 90 ∘ C.

Thermal performance of a novel helically coiled oscillating heat pipe (HCOHP) for isothermal adsorption. An experimental study

“…The helically coiled evaporator and condenser sections coupled with the vertical orientation of the HCOHPs potentially gives the evaporators the capacity to hold more working fluid. As shown by Sriudom et al 16 , the characteristics of the helical coil such as the pitch distance influences flow pattern percentage with an increased in pitch distance increasing stratified wavy flow pattern percentage in helical OHPs. According to Khandekar et al 50 , the performance independence of Closed Loop Pulsating Heat Pipes (CLPHP) with orientation is affected by the number of turns.…”

“…Chien et al 15 carried out an experimental investigation on a closed loop PHP (CLPHP) with non-uniform channel configuration designed to introduce additional unbalancing capillary force aimed at resolving problems with fewer turn PHPs in horizontal orientation and found the non-uniform channel CLPHP functioned at all inclinations when the charge ratio was above 50%. Sriudom et al 16 developed a helical oscillating heat pipe (HOHP) to investigate its flow behaviours and complicated phenomena of flow patterns and heat transfer characteristics. Their design was such that the coils for the evaporator and condenser were in a series arrangement and returned through the coils again to form the adiabatic section.…”

Three-dimensional transient mathematical model to predict the heat transfer rate of a heat pipe

“…The calculation procedure of the simulation program was as follows: First, the grids were generated. Second, the boundary conditions of the outer wall temperature were determined using equations (13) and (14), and the temperature along the pipe wall was calculated by equation (1). Next, the velocity profiles of the vapor phase at the vapor core were calculated using equations (2)-(6).…”

“…Determining the heat transfer rate was found by using this equation Q = _ mc p (T out À T in ). 14,15 The experimental setup with the test rig is shown in Figure 4, and photographic view of the experimental setup is shown in Figure 5. …”

Correlation for Predicting Heat Transfer Characteristics of A Helical Oscillating Heat Pipe (HOHP) at Normal Operating Conditions

“…The flow behaviors and complicated phenomena of flow patterns have not been covered nor specified (Yi et al 2003). (Sriudom et al 2014) studied the flow pattern behavior of a HOHP and the complicated phenomena of flow patterns were not covered or specified. They found four internal flow patterns namely bubble flow, slug flow, annular flow, and stratified wavy flow.…”