Theoretical investigation of the thermal performance of evacuated heat pipe solar collector with optimum tilt angle under various operating conditions

A two-dimensional mathematical model was developed for predicting the performance of an open-type water-cooled flat-plate solar collector, and solved numerically through an implicit finite difference method. The effects of various environmental and geometric conditions on energy absorption for the collector were investigated. The results predict that there is an optimum length and tilt angle for the absorbing plate for which the collector could obtain the highest solar energy absorptance. The latent heat flux of water evaporation can be 3 to 15 times larger than the sensible heat flux under normal operating conditions. The wind speed and the inlet water temperature have a large influence on the energy absorption of the collector. The effects of the solar incident flux, the atmospheric humidity and temperature, the absorbing plate tilt angle and length, and the water film thickness on the temperature rise of the water film and/or the absorptance of the collector are clarified. The open-type flat-plate collector is suitable to operate at lower inlet water temperatures and in regions where the local latitude is in the range of 20°N-40°N, and the weather is humid and hot with low winds. [S0199-6231(00)00202-1]

Download Full-text

06/02334 Developing a theoretical model to investigate thermal performance of a thin membrane heat-pipe solar collector

Fuel and Energy Abstracts ◽

10.1016/s0140-6701(06)82342-8 ◽

2006 ◽

Vol 47 (5) ◽

pp. 355

Keyword(s):

Theoretical Model ◽

Heat Pipe ◽

Thermal Performance ◽

Solar Collector ◽

Thin Membrane

Download Full-text

Advanced Cooling With Embedded Heat Pipes for High Power Microelectronics

ASME 2009 InterPACK Conference, Volume 2 ◽

10.1115/interpack2009-89111 ◽

2009 ◽

Cited By ~ 1

Author(s):

Victor Adrian Chiriac

Keyword(s):

Heat Pipe ◽

Thermal Performance ◽

Heat Sink ◽

Heat Pipes ◽

Optimal Operation ◽

Operating Conditions ◽

Peak Temperature ◽

Transient Temperature ◽

Efficient Operation ◽

The Impact

The transient thermal behavior of a complex testing system including multiple fans, a mixing enclosure, Cu inserts and a leaded package dissipating large amounts of power over short time durations is evaluated via numerical simulations. The system performance is optimized with heat sink/fan structure for device efficient operation under constant powering. The study provides meaningful understanding and prediction of a transient powering scenario at high powering levels, evaluating the impact of alternative cooling fan/heat pipe configurations on the thermal performance of the system. One design is chosen due to its effective thermal performance and assembly simplicity, with the package embedded in heat sink base with multiple (5) heat pipes. The peak temperature reached by the modified design with 4 cooling fans is ∼95°C, with the corresponding Rja thermal resistance ∼0.58°C/W. For the transient study (with embedded heat pipes and 4 fans), after one cycle, both peak temperature (at 45 s) and the end temperature (at 49 s) decrease as compared to the previous no heat pipe/single fan case (especially the end temperature reduces by ∼16%). The temperature drop between peak and end for each cycle is ∼80.2°C, while the average power per transient cycle is ∼31.27W. With this power, the design with 5 perpendicular heat pipes, 4 fans and insert reaches a steady state peak temperature of ∼98°C. Applying the superposition principle, the maximum transient temperature after a large number of operating cycles will not exceed ∼138.1°C, satisfying the thermal budget under the current operating conditions. The benefit of the study is related to the possibility to extract the maximum/minimum temperatures for a real test involving a large number of heating-cooling cycles, yet maintaining the initial and peak temperatures within a certain range for the optimal operation of the device. The flow and heat transfer fields are thoroughly investigated: using a combination of numerical and analytical study, the thermal performance of the device undergoing large number of periodic thermal cycles is predicted. Further comparison between measurement and simulation results reveals good agreement.

Download Full-text

Thermal performance prediction of heat pipe with TiO2 nanofluids using RSM

Thermal Science ◽

10.2298/tsci201229199r ◽

2021 ◽

pp. 199-199

Author(s):

Lakshmi Reddy ◽

Srinivasa Bayyapureddy Reddy ◽

Kakumani Govindarajulu

Keyword(s):

Heat Transfer ◽

Heat Transfer Coefficient ◽

Thermal Resistance ◽

Transfer Coefficient ◽

Heat Pipe ◽

Thermal Performance ◽

Tilt Angle ◽

Heat Load ◽

Maximum Heat ◽

Maximum Heat Transfer

Heat pipe is a two phase heat transfer device with high effective thermal conductivity and transfer huge amount of heat with minimum temperature gradient in between evaporator and condenser section. This paper objective is to predict the thermal performance in terms of thermal resistance (R) and heat transfer coefficient (h) of screen mesh wick heat pipe with DI water-TiO2 as working fluid. The input process parameters of heat pipe such as heat load (Q), tilt angle (?) and concentration of nanofluid (?) were modeled and optimized by utilizing Response Surface Methodology (RSM) with MiniTab-17 software to attain minimum thermal resistance and maximum heat transfer coefficient. The minimum thermal resistance of 0.1764 0C/W and maximum heat transfer coefficient of 1411.52 W/m2 0C was obtained under the optimized conditions of 200 W heat load, 57.20 tilt angle and 0.159 vol. % concentration of nano-fluid.

Download Full-text

Thermal Assessment of Cooling System Incorporating Heat Sink and Embedded Heat Pipes for Testing High Power Microelectronics

Heat Transfer, Part A ◽

10.1115/imece2005-81794 ◽

2005 ◽

Author(s):

Victor Adrian Chiriac ◽

Tien-Yu Tom Lee

Keyword(s):

Steady State ◽

Heat Pipe ◽

Thermal Performance ◽

Heat Sink ◽

Heat Pipes ◽

Optimal Operation ◽

Operating Conditions ◽

Peak Temperature ◽

Testing System ◽

The Impact

A numerical study was conducted to model the transient thermal behavior of a complex testing system including multiple fans, a mixing enclosure, copper inserts and a leaded package dissipating large amounts of power over short time durations. The system is optimized by choosing appropriate heat sink/fan structure for the efficient operation of the device under constant powering. The intent of the study is to provide a better understanding and prediction of a transient powering scenario at high powering levels, while evaluating the impact of alternative cooling fan/heat pipe designs on the thermal performance of the testing system. One design is chosen due to its effective thermal performance and assembly simplicity, with the package embedded in heat sink base with multiple (5) heat pipes. The peak temperature reached by the modified design with 4 cooling fans is ~95°C, with the corresponding Rja thermal resistance ~0.58°C/W. For the transient study (with embedded heat pipes and 4 fans), after one cycle, both peak temperature (at 45 s) and the end temperature (at 49 s) decrease as compared to the previous no heat pipe/single fan case (the end temperature reduces by ~16%). The temperature drop between peak and end for each cycle is ~80.2°C, while the average power per transient cycle is ~31.27W. With this power, the design with 5 perpendicular heat pipes, 4 fans and insert reaches a steady state peak temperature of ~98°C. Applying the superposition principle to the steady state value and 40.1°C fluctuation, the maximum transient temperature after a large number of cycles will not exceed ~138.1°C, satisfying the thermal budget under the current operating conditions. The benefit of the study is related to the possibility to extract the maximum and minimum temperatures for a real test involving a large number of heating-cooling cycles, yet maintaining the initial and peak temperatures within a certain range for the optimal operation of the device. The flow and heat transfer fields are investigated; using a combination of numerical and analytical methods, the thermal performance of the device undergoing large number of periodic thermal cycles is predicted. The comparison between measurement and simulation shows good agreement.

Download Full-text