Cavity receiver thermal performance analysis based on total heat loss coefficient and efficiency factor

2018 ◽  
Vol 42 (6) ◽  
pp. 2284-2289 ◽  
Author(s):  
Qiangqiang Zhang ◽  
Xin Li ◽  
Zhifeng Wang ◽  
Zhi Li ◽  
Hong Liu ◽  
...  
Keyword(s):  
Performance Analysis ◽  
Heat Loss ◽  
Thermal Performance ◽  
Efficiency Factor ◽  
Loss Coefficient ◽  
Total Heat ◽  
Total Heat Loss

scholarly journals Effects of Absorber Emissivity on Thermal Performance of a Solar Cavity Receiver

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
Jiabin Fang ◽  
Nan Tu ◽  
Jinjia Wei
Keyword(s):  
Heat Loss ◽  
Thermal Performance ◽  
Thermal Efficiency ◽  
Radiative Heat ◽  
Slight Effect ◽  
Radiative Heat Loss ◽  
Total Heat Loss ◽  
Convective Heat Loss ◽  
Performance Curves ◽  
Variation Tendency

Solar cavity receiver is a key component to realize the light-heat conversion in tower-type solar power system. It usually has an aperture for concentrated sunlight coming in, and the heat loss is unavoidable because of this aperture. Generally, in order to improve the thermal efficiency, a layer of coating having high absorptivity for sunlight would be covered on the surface of the absorber tubes inside the cavity receiver. As a result, it is necessary to investigate the effects of the emissivity of absorber tubes on the thermal performance of the receiver. In the present work, the thermal performances of the receiver with different absorber emissivity were numerically simulated. The results showed that the thermal efficiency increases and the total heat loss decreases with increasing emissivity of absorber tubes. However, the thermal efficiency increases by only 1.6% when the emissivity of tubes varies from 0.2 to 0.8. Therefore, the change of absorber emissivity has slight effect on the thermal performance of the receiver. The reason for variation tendency of performance curves was also carefully analyzed. It was found that the temperature reduction of the cavity walls causes the decrease of the radiative heat loss and the convective heat loss.

scholarly journals Fitness-related differences in the rate of whole-body total heat loss in exercising young healthy women are heat-load dependent

2018 ◽  
Vol 103 (3) ◽  
pp. 312-317 ◽  
Author(s):  
Dallon T. Lamarche ◽  
Sean R. Notley ◽  
Martin P. Poirier ◽  
Glen P. Kenny
Keyword(s):  
Heat Loss ◽  
Heat Load ◽  
Total Heat ◽  
Whole Body ◽  
Total Heat Loss ◽  
Healthy Women

scholarly journals Heat loss analysis of three coil cylindrical solar cavity receiver of parabolic dish for process heat

2019 ◽  
Vol 23 (Suppl. 4) ◽  
pp. 1301-1310
Author(s):  
Ramola Sinha ◽  
Nitin Gulhane ◽  
Jan Taler ◽  
Pawel Oclon
Keyword(s):  
Cost Effectiveness ◽  
Heat Loss ◽  
Total Heat ◽  
Fluid Temperature ◽  
Total Heat Loss ◽  
Wall Area ◽  
Single Coil ◽  
Receiver System ◽  
Parabolic Dish ◽  
Process Heat

The share of solar thermal energy for process heat at sub cooled temperature is estimated about 30% of the total demand. The assessment of heat loss from tubular receiver used for the process heat is necessary to improve the thermal efficiency and consequently the cost effectiveness of the parabolic dish receiver system. The study considers a modified three coil solar cavity receiver of wall area three times (approximately) as compared to the existing single coil receiver and experimentally investigates the effect of increases in cavity inner wall area, fluid inlet temperature (50-75?C), and cavity inclination angle (? = 0-90?) on the combined (total) heat loss from receiver under no wind condition. This paper also develops an analytical model to estimate the different mode of heat losses from the downward facing receiver. In the mean fluid temperature range of 50?C to 70?C, the total heat loss from three coil receiver is reduced up to 40.98% at 90? and 20% at 0? inclination, as compared to single coil receiver. The analytical modeling estimates very low heat loss from conduction (1-3%) and radiation (2-8%) and high heat loss from convection (97-89%). The heat loss by natural convection decreases sharply with increase in cavity inclination, while the heat loss by radiation and conduction increases slowly with inclination. A three coil cavity receiver might be considered in the design to reduce heat loss from parabolic dish receiver system to improve the thermal performance and cost effectiveness.

A Comparative Numerical Study on Conjugate Natural Convection From Vertical Hollow Cylinder With Finite Thickness Placed on Ground and in Air

2020 ◽  
Vol 13 (2) ◽  
Author(s):  
Manoj Kumar Dash ◽  
Sukanta Kumar Dash
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Natural Convection ◽  
Heat Loss ◽  
Hollow Cylinder ◽  
Average Nusselt Number ◽  
Total Heat ◽  
Outer Diameter ◽  
Thermal Plume ◽  
Total Heat Loss

Abstract The present work reports a comparative analysis of natural convection heat transfer from a thick hollow vertical cylinder either placed on the ground or suspended in the air. The numerical simulations have been performed by varying the cylinder length to its outer diameter (L/Do) in the range of 0.2–20, the thickness ratio (Di/Do) in a range of 0.5–0.9, and Rayleigh number (Ra) from 104 to 108. The flow and heat transfer characteristics have been delineated precisely with the presentation of the thermal plume and flow field in the vicinity of the cylinder. The variation of average Nusselt number (Nu), local Nu, and contribution to total heat loss from different surfaces with the pertinent parameters have been elucidated graphically. The average Nu is always more for the cylinder in the air compared with the case when it is on the ground. However, the difference between the Nu for these two cases diminishes, as the L/Do increases. It has also been found that the contribution to total heat loss from the inner surface of the hollow cylinder suspended in air increases with L/Do, attains a peak, and decreases sharply. Cooling time curves for the cylinder placed in air or on the ground have been described precisely. Finally, a correlation for the average Nusselt number as a function of all the pertinent parameters has been proposed that can be useful for industrial and academic purposes.

scholarly journals Self-reported physical activity level does not alter whole-body total heat loss independently of aerobic fitness in young adults during exercise in the heat

2019 ◽  
Vol 44 (1) ◽  
pp. 99-102 ◽  
Author(s):  
Dallon T. Lamarche ◽  
Sean R. Notley ◽  
Martin P. Poirier ◽  
Glen P. Kenny
Keyword(s):  
Physical Activity ◽  
Young Adults ◽  
Oxygen Consumption ◽  
Heat Loss ◽  
Aerobic Fitness ◽  
Total Heat ◽  
Activity Level ◽  
Peak Oxygen Consumption ◽  
Whole Body ◽  
Total Heat Loss

We evaluated whether self-reported physical activity (PA) level modulates whole-body total heat loss (WB-THL) as assessed using direct calorimetry in 10 young adults (aged 22 ± 3 years) matched for rate of peak oxygen consumption (an index for aerobic fitness), but of low and high self-reported PA, during 3 incremental cycling bouts (∼39%, 52%, and 64% peak oxygen consumption) in the heat (40 °C). We showed that level of self-reported PA does not appear to influence WB-THL independently of peak oxygen consumption.

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