scholarly journals Experimentation of a Wearable Self-Powered Jacket Harvesting Body Heat for Wearable Device Applications

2021 ◽  
Vol 2021 ◽  
pp. 1-22
Author(s):  
Atif Sardar Khan ◽  
Farid Ullah Khan
Keyword(s):  
Heat Transfer ◽  
Power Generation ◽  
Heat Transfer Coefficient ◽  
Thermal Resistance ◽  
Transfer Coefficient ◽  
Heat Sink ◽  
Energy Harvester ◽  
Wearable Devices ◽  
Cold Side ◽  
Self Powered

The development of special wearable/portable electronic devices for health monitoring is rapidly growing to cope with different health parameters. The emergence of wearable devices and its growing demand has widened the scope of self-powered wearable devices with the possibility to eliminate batteries. For instance, the wearable thermoelectric energy harvester (TEEH) is an alternate to batteries, which has been used in this study to develop four different self-powered wearable jacket prototypes and experimentally validated. It is observed that the thermal resistance of the cold side without a heat sink of prototype 4 is much greater than the rest of the proposed prototypes. Besides that, the thermal resistance of prototype 4 heat sinks is even lower among all proposed prototypes. Therefore, prototype 4 would have a relatively higher heat transfer coefficient which results in improved power generation. Moreover, an increase in heat transfer coefficient is observed with an increase in the temperature difference of the cold and hot sides of a TEEH. Thus, on the cold side, a heat flow increases which benefits heat dissipation and in turn reduces the thermal resistance of the heat sink. Besides that, the developed prototypes on people show that power generation is also affected by factors like ambient temperature, person’s activity, and wind breeze and does not depend on the metabolism. A different mechanism has been explored to maximize the power output within a 16.0 cm2 area, in order to justify the wearability of the energy harvester. Furthermore, it is observed that during the sunlight, any material covering the TEEH would improve the performance of prototypes. Prototypes are integrated into jacket and studied extensively. The TEEH system was designed to produce a maximum delivering power and power density of 699.71 μW and 43.73 μW/cm2, respectively. Moreover, the maximum voltage produced is 62.6 mV at an optimal load of 5.6 Ω. Furthermore, the TEEH (prototype 4) is connected to a power management circuit of ECT310 and LTC3108 and has been able to power 18 LEDs.

Convection Calibration of Schmidt–Boelter Heat Flux Gauges in Stagnation and Shear Air Flow

2009 ◽  
Vol 132 (3) ◽  
Author(s):  
A. Gifford ◽  
A. Hoffie ◽  
T. Diller ◽  
S. Huxtable
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Shear Flow ◽  
Thermal Resistance ◽  
Transfer Coefficient ◽  
Heat Sink ◽  
Nonlinear Dependence ◽  
Stagnation Flow ◽  
Internal Thermal Resistance

Experiments were performed to characterize the performance of Schmidt–Boelter heat flux gauges in stagnation and shear convective air flows. The gauges were of a standard design (25.4 mm and 38 mm in diameter), using a copper heat sink with water cooling channels around the active sensing element. A simple model of the gauges using an internal thermal resistance between the sensor surface and the heat sink is used to interpret the results. The model predicts a nonlinear dependence of the gauge sensitivity as a function of the heat transfer coefficient. Experimental calibration systems were developed to simultaneously measure the heat flux gauge response relative to a secondary standard under the same flow and thermal conditions. The measured gauge sensitivities in the stagnation flow matched the model, and were used to estimate the value of the internal thermal resistance for each of the four gauges tested. For shear flow, the effect of the varying gauge surface temperature on the boundary layer was included. The results matched the model with a constant factor of 15–25% lower effective heat transfer coefficient. When the gauge was water cooled, the effect of the internal thermal resistance of the gauge was markedly different for the two flow conditions. In the stagnation flow, the internal resistance further decreased the apparent gauge sensitivity. Conversely, in shear flow, the resistance was effectively offset by the cooler heat sink of the gauge, and the resulting sensitivities were nearly the same as, or larger than, for radiation.

Experimental and theoretical investigation of heat transfer characteristics of cylindrical heat pipe using Al2O3–SiO2/W-EG hybrid nanofluids by RSM modeling approach

2021 ◽  
Vol 68 (1) ◽  
Author(s):  
R. Vidhya ◽  
T. Balakrishnan ◽  
B. Suresh Kumar
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Heat Transfer Coefficient ◽  
Thermal Resistance ◽  
Transfer Coefficient ◽  
Heat Pipe ◽  
Diffraction Spectrum ◽  
Step Method ◽  
Ceramic Nanoparticles ◽  
Transfer Mechanisms

AbstractNanofluids are emerging two-phase thermal fluids that play a vital part in heat exchangers owing to its heat transfer features. Ceramic nanoparticles aluminium oxide (Al2O3) and silicon dioxide (SiO2) were produced by the sol-gel technique. Characterizations have been done through powder X-ray diffraction spectrum and scanning electron microscopy analysis. Subsequently, few volume concentrations (0.0125–0.1%) of hybrid Al2O3–SiO2 nanofluids were formulated via dispersing both ceramic nanoparticles considered at 50:50 ratio into base fluid combination of 60% distilled water (W) with 40% ethylene glycol (EG) using an ultrasonic-assisted two-step method. Thermal resistance besides heat transfer coefficient have been examined with cylindrical mesh heat pipe reveals that the rise of power input decreases the thermal resistance and inversely increases heat transfer coefficient about 5.54% and 43.16% respectively. Response surface methodology (RSM) has been employed for the investigation of heat pipe experimental data. The significant factors on the various convective heat transfer mechanisms have been identified using the analysis of variance (ANOVA) tool. Finally, the empirical models were developed to forecast the heat transfer mechanisms by regression analysis and validated with experimental data which exposed the models have the best agreement with experimental results.

Flow Boiling Heat Transfer in a Silicon Microchannel Heat Sink Using Liquid Crystal Thermography

2008 ◽  
Author(s):  
Ayman Megahed ◽  
Ibrahim Hassan ◽  
Tariq Ahmad
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Heat Sink ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Heat Fluxes ◽  
Working Fluid ◽  
Microchannel Heat Sink

The present study focuses on the experimental investigation of boiling heat transfer characteristics and pressure drop in a silicon microchannel heat sink. The microchannel heat sink consists of a rectangular silicon chip in which 45 rectangular microchannels were chemically etched with a depth of 295 μm, width of 254 μm, and a length of 16 mm. Un-encapsulated Thermochromic liquid Crystals (TLC) are used in the present work to enable nonintrusive and high spatial resolution temperature measurements. This measuring technique is used to provide accurate full and local surface-temperature and heat transfer coefficient measurements. Experiments are carried out for mass velocities ranging between 290 to 457 kg/m2.s and heat fluxes from 6.04 to 13.06 W/cm2 using FC-72 as the working fluid. Experimental results show that the pressure drop increases as the exit quality and the flow rate increase. High values of heat transfer coefficient can be obtained at low exit quality (xe < 0.2). However, the heat transfer coefficient decreases sharply and remains almost constant as the quality increases for an exit quality higher than 0.2.

Optimization Under Uncertainty of Manifold Microchannel Heat Sinks

2012 ◽  
Author(s):  
Suchismita Sarangi ◽  
Karthik K. Bodla ◽  
Suresh V. Garimella ◽  
Jayathi Y. Murthy
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Heat Sink ◽  
Heat Sinks ◽  
Optimization Under Uncertainty ◽  
Microchannel Heat Sink ◽  
Probabilistic Optimization ◽  
Manifold Microchannel

Conventional microchannel heat sinks provide good heat dissipation capability but are associated with high pressure drop and corresponding pumping power. The use of a manifold system that distributes the flow into the microchannels through multiple, alternating inlet and outlet pairs is investigated here. This manifold arrangement greatly reduces the pressure drop incurred due to the smaller flow paths, while simultaneously increasing the heat transfer coefficient by tripping the thermal boundary layers. A three-dimensional numerical model is developed and validated, to study the effect of various geometric parameters on the performance of the manifold microchannel heat sink. Apart from a deterministic analysis, a probabilistic optimization study is also performed. In the presence of uncertainties in the geometric and operating parameters of the system, this probabilistic optimization approach yields an optimal design that is also robust and reliable. Uncertainty-based optimization also yields auxiliary information regarding local and global sensitivities and helps identify the input parameters to which outputs are most sensitive. This information can be used to design improved experiments targeted at the most sensitive inputs. Optimization under uncertainty also provides a quantitative estimate of the allowable uncertainty in input parameters for an acceptable uncertainty in the relevant output parameters. The optimal geometric design parameters with uncertainties that maximize heat transfer coefficient while minimizing pressure drop for fixed input conditions are identified for a manifold microchannel heat sink. A comparison between the deterministic and probabilistic optimization results is also presented.

Heat transfer coefficient of nanofluids in minichannel heat sink

2012 ◽  
Author(s):  
Adi T. Utomo ◽  
Ashkan I. T. Zavareh ◽  
Heiko Poth ◽  
Mohd Wahab ◽  
Mohammad Boonie ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Heat Sink

Thermal Characteristics of a Cylindrical Heat Pipe using Multi-Layer Screen Mesh Wick

2018 ◽  
Vol 10 (5) ◽  
Author(s):  
R. Sankar Rao ◽  
S. Bhanu Prakash
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Thermal Resistance ◽  
Transfer Coefficient ◽  
Heat Pipe ◽  
Thermal Characteristics ◽  
Wire Mesh ◽  
Working Fluid ◽  
Wick Structure ◽  
Screen Mesh

Heat pipe is the most widely used heat exchanging device in removal of heat from any given system at a faster rate. The thermal characteristics of heat pipe with single and multi-layered screen mesh wicks have been observed with two working fluids water and acetone. Heat pipe of length 250 mm and 12.7 mm outer diameter, made of copper material is used in all the trials of with and without wick structure. A 100 mesh stainless steel screen wire mesh is chosen as wick structure. Experiments were conducted at different heat loads and various inclinations with 100% fill ratio in evaporator. The performance is measured based on total thermal resistance and overall heat transfer coefficient. The heat pipe is found effective at 60o inclination with acetone as a working fluid and with four layered screen mesh wick. Uncertainty in thermal resistance and heat transfer coefficient is calculated for a heat input of 10W at 0 and 60 inclinations.

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