Experimental comparison of summer thermal performance of green roof (GR), double skin roof (DSR) and cool roof (CR) in lightweight rooms in subtropical climate

2021 ◽  
pp. 174425912110405
Author(s):  
Erlin Meng ◽  
Jiawang Yang ◽  
Ruonan Cai ◽  
Bo Zhou ◽  
Junqi Wang
Keyword(s):  
Heat Flux ◽  
Solar Radiation ◽  
Thermal Performance ◽  
Surface Heat Flux ◽  
Internal Surface ◽  
Surface Heat ◽  
Experimental Comparison ◽  
Subtropical Climate ◽  
Weather Factors ◽  
Solar Altitude

Subtropical climate is characterized by high solar altitude angle in summer which causes the roof get more heat through solar radiation. GR, DSR, and CR all can decrease solar radiation heat gain of the roof. However, few researches have been done to the comparison of the thermal performance of these three roofs, especially in subtropical climate. In this study, four rooms were built separately with GR, DSR, CR, and ordinary roof (OR). The experiment was done from July 23 to August 4. Results showed that stabilities of the indoor air temperature of the four rooms were: DSR room > GR room > CR room > OR room. The GR, CR, and DSR can reduce the external surface temperature by 13.7°C, 12.0°C, and 4.8°C during the day while bring a temperature rise of 2.3°C, 1.9°C, and 0.9°C at night. Correlation analysis results showed that the internal surface heat flux of GR and DSR were negative correlated with weather factors while internal surface heat flux of OR and CR were positive correlated with weather factors. This study can give support to the selection between GR, DSR, and CR.

Fuzzy Identification of the Time- and Space-Dependent Internal Surface Heat Flux of Slab Continuous Casting Mold

2018 ◽  
Vol 140 (12) ◽  
Author(s):  
Guangjun Wang ◽  
Shibin Wan ◽  
Hong Chen ◽  
Kun Wang ◽  
Cai Lv
Keyword(s):  
Heat Flux ◽  
Continuous Casting ◽  
Surface Heat Flux ◽  
Fuzzy Inference ◽  
Internal Surface ◽  
Surface Heat ◽  
Normal Distribution Function ◽  
Continuous Casting Mold ◽  
Time And Space ◽  
Casting Mold

To identify the transient and distributed internal surface heat flux of the slab mold in continuous casting process, a fuzzy inference method is proposed in this work. For temporal and spatial distribution characteristics of the internal surface heat flux of continuous casting mold, a decentralized fuzzy inference (DFI) identification scheme possessed of a decoupling characteristic in time and space is established. For each temperature measurement point, the fuzzy inference processes are, respectively, executed from the correspondingly observed temperature sequence through corresponding DFI units. In the time domain, according to sensitivity coefficients, the weighing and synthesizing processes for the decentralized inference results are performed to get the temporal compensation vector for the internal surface heat flux of mold. Then, in the space domain, according to the normal distribution function, the weighing and synthesizing processes for the temporal compensation vectors are performed to get the spatial compensation vector for the internal surface heat flux of mold. Numerical tests are carried out to research the influence of the number of thermocouples and measurement errors on the identification results, which prove the effectiveness of proposed scheme in this work.

Thermal Behavior of Double Glass Window Filled with Absorbing and Non-Absorbing Gas

2013 ◽  
Vol 805-806 ◽  
pp. 1603-1611 ◽  
Author(s):  
Chun Li Tang ◽  
Xiao Wei Zhang
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Solar Radiation ◽  
Free Convection ◽  
Surface Heat Flux ◽  
Radiation Flux ◽  
Surface Heat ◽  
Solar Radiation Flux ◽  
Surface Heat Transfer Coefficient

This paper presents a radiant model based on the radiant resistance analysis theory and the results of numerical simulations of double glass window. The two-dimensional steady state model is formulated based upon the radiation and free convection heat transfer at different external and internal ambient conditions.The properties of glass which change with incident wavelength are also considered. Specifically, air and CO2 are used as the medium in the 8mm and 10mm cavity of the double glass window, respectively. Several parameters, including transmitted solar radiation flux, temperature distribution, surface heat transfer coefficient for free convection and total surface heat flux are calculated. The results show that transmitted solar radiation flux is slightly lower when filled with CO2 in the cavity than with air due to their absorption difference. Also, the temperature of gas closing to internal glass sheet and the total surface heat flux of internal glass sheet are decreased when filled with CO2 than with air, although the surface heat transfer coefficient is slightly higher when it is CO2. .The temperature variation curves show that less heat flows into the room when filled with CO2 than air in double glass window.

scholarly journals Uncertainty in Net Surface Heat Flux due to Differences in Commonly Used Albedo Products

2020 ◽  
Vol 33 (1) ◽  
pp. 303-315
Author(s):  
Allison Hogikyan ◽  
Meghan F. Cronin ◽  
Dongxiao Zhang ◽  
Seiji Kato
Keyword(s):  
Heat Flux ◽  
High Resolution ◽  
Solar Radiation ◽  
Surface Heat Flux ◽  
Radiant Energy ◽  
Ocean Surface ◽  
Surface Heat ◽  
Surface Energy Budget ◽  
Spatiotemporal Variability ◽  
Shortwave Radiation

AbstractThe ocean surface albedo is responsible for the distribution of solar (shortwave) radiant energy between the atmosphere and ocean and therefore is a key parameter in Earth’s surface energy budget. In situ ocean observations typically do not measure upward reflected solar radiation, which is necessary to compute net solar radiation into the ocean. Instead, the upward component is computed from the measured downward component using an albedo estimate. At two NOAA Ocean Climate Station buoy sites in the North Pacific, the International Satellite Cloud Climatology Project (ISCCP) monthly climatological albedo has been used, while for the NOAA Global Tropical Buoy Array a constant albedo is used. This constant albedo is also used in the Coupled Ocean–Atmosphere Response Experiment (COARE) bulk flux algorithm. This study considers the impacts of using the more recently available NASA Cloud and the Earth’s Radiant Energy System (CERES) albedo product for these ocean surface heat flux products. Differences between albedo estimates in global satellite products like these imply uncertainty in the net surface solar radiation heat flux estimates that locally exceed the target uncertainty of 1.0 W m−2 for the global mean, set by the Global Climate Observing System (GCOS) of the World Meteorological Organization (WMO). Albedo has large spatiotemporal variability on hourly, monthly, and interannual time scales. Biases in high-resolution SWnet (the difference between surface downwelling and upwelling shortwave radiation) can arise if the albedo diurnal cycle is unresolved. As a result, for periods when satellite albedo data are not available it is recommended that an hourly climatology be used when computing high-resolution net surface shortwave radiation.

Analysis of significant measures for thermal conductivity

2020 ◽  
pp. 35-42
Author(s):  
Yuri P. Zarichnyak ◽  
Vyacheslav P. Khodunkov
Keyword(s):  
Thermal Conductivity ◽  
Heat Flux ◽  
Surface Heat Flux ◽  
Heat Flux Density ◽  
Measurement Method ◽  
Conductivity Measurement ◽  
Surface Heat ◽  
Measuring Instrument ◽  
New Class ◽  
Achievable Accuracy

The analysis of a new class of measuring instrument for heat quantities based on the use of multi-valued measures of heat conductivity of solids. For example, measuring thermal conductivity of solids shown the fallacy of the proposed approach and the illegality of the use of the principle of ambiguity to intensive thermal quantities. As a proof of the error of the approach, the relations for the thermal conductivities of the component elements of a heat pump that implements a multi-valued measure of thermal conductivity are given, and the limiting cases are considered. In two ways, it is established that the thermal conductivity of the specified measure does not depend on the value of the supplied heat flow. It is shown that the declared accuracy of the thermal conductivity measurement method does not correspond to the actual achievable accuracy values and the standard for the unit of surface heat flux density GET 172-2016. The estimation of the currently achievable accuracy of measuring the thermal conductivity of solids is given. The directions of further research and possible solutions to the problem are given.

Heat Transfer Characteristics of Downward Facing Hot Horizontal Surfaces Using Mist Jet Impingement

2017 ◽  
Author(s):  
Ashutosh Kumar Yadav ◽  
Parantak Sharma ◽  
Avadhesh Kumar Sharma ◽  
Mayank Modak ◽  
Vishal Nirgude ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Surface Heat Flux ◽  
Cooling System ◽  
Water Pressure ◽  
Jet Impingement ◽  
Surface Heat ◽  
Heat Transfer Characteristics ◽  
Impingement Cooling ◽  
Transfer Characteristics

Impinging jet cooling technique has been widely used extensively in various industrial processes, namely, cooling and drying of films and papers, processing of metals and glasses, cooling of gas turbine blades and most recently cooling of various components of electronic devices. Due to high heat removal rate the jet impingement cooling of the hot surfaces is being used in nuclear industries. During the loss of coolant accidents (LOCA) in nuclear power plant, an emergency core cooling system (ECCS) cool the cluster of clad tubes using consisting of fuel rods. Controlled cooling, as an important procedure of thermal-mechanical control processing technology, is helpful to improve the microstructure and mechanical properties of steel. In industries for heat transfer efficiency and homogeneous cooling performance which usually requires a jet impingement with improved heat transfer capacity and controllability. It provides better cooling in comparison to air. Rapid quenching by water jet, sometimes, may lead to formation of cracks and poor ductility to the quenched surface. Spray and mist jet impingement offers an alternative method to uncontrolled rapid cooling, particularly in steel and electronics industries. Mist jet impingement cooling of downward facing hot surface has not been extensively studied in the literature. The present experimental study analyzes the heat transfer characteristics a 0.15mm thick hot horizontal stainless steel (SS-304) foil using Internal mixing full cone (spray angle 20 deg) mist nozzle from the bottom side. Experiments have been performed for the varied range of water pressure (0.7–4.0 bar) and air pressure (0.4–5.8 bar). The effect of water and air inlet pressures, on the surface heat flux has been examined in this study. The maximum surface heat flux is achieved at stagnation point and is not affected by the change in nozzle to plate distance, Air and Water flow rates.

scholarly journals Nanofluid Flow on a Shrinking Cylinder with Al2O3 Nanoparticles

Mathematics ◽  
2021 ◽  
Vol 9 (14) ◽  
pp. 1612
Author(s):  
Iskandar Waini ◽  
Anuar Ishak ◽  
Ioan Pop
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Friction Factor ◽  
Surface Heat Flux ◽  
Transfer Rate ◽  
Surface Heat ◽  
Al2o3 Nanoparticles ◽  
Nanofluid Flow ◽  
Curvature Parameter ◽  
Over Time

This study investigates the nanofluid flow towards a shrinking cylinder consisting of Al2O3 nanoparticles. Here, the flow is subjected to prescribed surface heat flux. The similarity variables are employed to gain the similarity equations. These equations are solved via the bvp4c solver. From the findings, a unique solution is found for the shrinking strength λ≥−1. Meanwhile, the dual solutions are observed when λc<λ<−1. Furthermore, the friction factor Rex1/2Cf and the heat transfer rate Rex−1/2Nux increase with the rise of Al2O3 nanoparticles φ and the curvature parameter γ. Quantitatively, the rates of heat transfer Rex−1/2Nux increase up to 3.87% when φ increases from 0 to 0.04, and 6.69% when γ increases from 0.05 to 0.2. Besides, the profiles of the temperature θ(η) and the velocity f’(η) on the first solution incline for larger γ, but their second solutions decline. Moreover, it is noticed that the streamlines are separated into two regions. Finally, it is found that the first solution is stable over time.

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