Experimental Measurement of Water Evaporation Rates Into Air and Superheated Steam

1988 ◽  
Vol 110 (1) ◽  
pp. 237-242 ◽  
Author(s):  
M. Haji ◽  
L. C. Chow
Keyword(s):  
Heat Transfer ◽  
Superheated Steam ◽  
Evaporation Rate ◽  
Free Stream ◽  
Experimental Results ◽  
Water Evaporation ◽  
Analytical Prediction ◽  
Conduction Heat Transfer ◽  
Inversion Temperature ◽  
Analytical Results

The rates of evaporation of water from a horizontal water surface into a turbulent stream of hot air or superheated steam at different free-stream mass fluxes and modulated temperatures were experimentally measured. The pressure of the free stream was atmospheric. For steam, the experimental results are mostly within 10 percent of the available analytical results. Two previous experimental results are about 50 percent and 300 percent higher than the analytical results. For air, the measured evaporation rates are consistently higher than the analytical results. An estimate of the conduction heat transfer from the walls of the test section to water was made for several air tests. If the conduction heat transfer were subtracted from the total heat transfer, the measured evaporation rates are actually quite close to the analytical results. The present experiment also confirms the existence of a temperature, called the inversion temperature, below which the water evaporation rate is higher in air than in steam, but above which the opposite is true. The inversion temperature is in good agreement with the analytical prediction. The results for both air and superheated steam show that a certain scaled expression for the evaporation rate is independent of the free-steam mass flux, also in agreement with the analytical prediction.

Thermal Management of Surface Mount Power Magnetic Components

1999 ◽  
Vol 122 (4) ◽  
pp. 323-327
Author(s):  
G. Refai-Ahmed ◽  
M. M. Yovanovich
Keyword(s):  
Heat Transfer ◽  
Power Loss ◽  
Numerical Study ◽  
Lower Surface ◽  
Experimental Results ◽  
Surface Mount ◽  
Conduction Heat Transfer ◽  
Magnetic Components ◽  
Underfill Material ◽  
Good Agreement

A numerical and experimental study of conduction heat transfer from low power magnetic components with gull wing leads was conducted to determine the effects of distributing the power loss between the core, the winding and the thermal underfill on the thermal resistance. The numerical study was conducted in the power loss ratio range of 0.5⩽PR⩽1.0, where the only active power loss was from the winding at PR=1. In addition, the effect of the thermal underfill material between the substrate and the lower surface of the magnetic package on the thermal performance of the magnetic device was also examined. For comparison, a test was conducted on a magnetic component at PR=1, without thermal underfill. This comparison revealed good agreement between the numerical and experimental results. Finally, a general model was proposed for conduction heat transfer from the surface mount power magnetic packages. The agreement between the model and the experimental results was within 8 percent. [S1043-7398(00)00704-0]

scholarly journals Modeling Microwave Heating and Drying of Lignocellulosic Foams through Coupled Electromagnetic and Heat Transfer Analysis

Processes ◽  
2021 ◽  
Vol 9 (11) ◽  
pp. 2001
Author(s):  
Mohammad Tauhiduzzaman ◽  
Islam Hafez ◽  
Douglas Bousfield ◽  
Mehdi Tajvidi
Keyword(s):  
Heat Transfer ◽  
Microwave Heating ◽  
Microwave Power ◽  
Expanded Polystyrene ◽  
Experimental Results ◽  
Microwave Drying ◽  
Heat Transfer Analysis ◽  
Water Evaporation ◽  
Time Behavior ◽  
Novel Method

Microwave drying of suspensions of lignocellulosic fibers has the potential to produce porous foam materials that can replace materials such as expanded polystyrene, but the design and control of this drying method are not well understood. The main objective of this study was to develop a microwave drying model capable of predicting moisture loss regardless of the shape and microwave power input. A microwave heating model was developed by coupling electromagnetic and heat transfer physics using a commercial finite element code. The modeling results predicted heating time behavior consistent with experimental results as influenced by electromagnetic fields, waveguide size and microwave power absorption. The microwave heating modeling accurately predicted average temperature increase for 100 cm3 water domain at 360 and 840 W microwave power inputs. By dividing the energy absorption by the heat of vaporization, the amount of water evaporation in a specific time increment was predicted leading to a novel method to predict drying. Using this method, the best time increments, and other parameters were determined to predict drying. This novel method predicts the time to dry cellulose foams for a range of sample shapes, parameters, material parameters. The model was in agreement with the experimental results.

Experimental Effects of Transverse Oscillations on Free Convection of a Vertical, Finite Plate

1964 ◽  
Vol 86 (2) ◽  
pp. 159-165 ◽  
Author(s):  
V. D. Blankenship ◽  
J. A. Clark
Keyword(s):  
Heat Transfer ◽  
Laminar Flow ◽  
Free Convection ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Experimental Results ◽  
Transverse Oscillation ◽  
Finite Plate ◽  
Analytical Results ◽  
Transverse Oscillations

The effects of transverse oscillation on free convection from a vertical, finite plate is investigated experimentally. This paper supplements an earlier paper wherein analytical results were reported. In that paper it was reported that oscillation slightly decreases the heat-transfer rate for laminar flow. The experimental results are in accord. However, more important is the fact that the oscillation forces the flow to become turbulent whereby large increases in heat-transfer rate are obtained. Experimental results are given for heat-transfer rate, both laminar and turbulent, and transition.

Improving the Performance and Energy Efficiency of Pneumatic Dryer for Okara

2017 ◽  
Vol 33 (5) ◽  
pp. 729-736 ◽  
Author(s):  
Chatchai Nimmol ◽  
Anucha Hirunwat
Keyword(s):  
Heat Transfer ◽  
Energy Efficiency ◽  
Heat Transfer Coefficient ◽  
Energy Consumption ◽  
Transfer Coefficient ◽  
Specific Energy ◽  
Evaporation Rate ◽  
Specific Energy Consumption ◽  
Water Evaporation ◽  
Drying Process

Abstract. A corrugated-pipe drying column and a multipass drying concept (one-pass and two-pass drying) were proposed in this study to improve the performance and energy efficiency of a conventional pneumatic dryer for okara. The performance (in terms of volumetric water evaporation rate and volumetric heat transfer coefficient) and the energy efficiency of the dryer were evaluated. With the use of the corrugated-pipe drying column, the moisture reduction of the okara, the volumetric water evaporation rate, and the volumetric heat transfer coefficient were enhanced. The specific energy consumption (SEC) of the drying process was also improved. The maximum values of the volumetric water evaporation rate and the volumetric heat transfer coefficient of 765 kgwater m-3 h-1 and 6966 W m-3 K-1, respectively, were found when drying was performed by the system using the corrugated-pipe drying column. The lowest value of the SEC of 3.03 MJ kgwater-1 was also observed. The lowest final moisture content of okara obtained after the two-pass drying was around 0.72 kgwater kgdrysolid-1. Keywords: Corrugated pipe, Multipass drying, Okara, Pneumatic dryer, Specific energy consumption, Volumetric heat transfer coefficient, Volumetric water evaporation rate.

Experimental Model to Characterize the Evaporative Cooling of Horizontal Roofs

2008 ◽  
Author(s):  
Margarita Gil Samaniego Ramos ◽  
He´ctor Enrique Campbell Rami´rez
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Mass Transfer ◽  
Evaporation Rate ◽  
Evaporative Cooling ◽  
Water Evaporation ◽  
Flat Plates ◽  
Transfer Rates ◽  
Dry Conditions ◽  
Models Validation

Heat and mass transfer models were developed experimentally to characterize the evaporative cooling of horizontal roofs, heated by thermal radiation. Surface temperatures of flat plates were evaluated at dry conditions and when humidified with water atomizers. For both conditions, heat transfer rates were calculated, and for the wet case also the mass transfer rates were predicted. Experimental data for models validation were measured at environmental and controlled conditions. Accuracies achieved were 2% for surface temperature and 13% for water evaporation rate.

Experimental investigation of the effects of intermediate gravity waves on the water evaporation rate

2021 ◽  
pp. 1-16
Author(s):  
Safa M Aldarabseh ◽  
Parviz Merati
Keyword(s):  
Water Surface ◽  
Evaporation Rate ◽  
Experimental Results ◽  
Wave Crest ◽  
Water Evaporation ◽  
Wave Steepness ◽  
Airflow Velocity ◽  
Wave Trough ◽  
Wide Range ◽  
Turbulent Airflow

Abstract This experiment was done to predict the evaporation rate from the wavy water surface under the different convection regimes ( free, forced, and mixed) at turbulent airflow conditions over a wide range of the ratio(Gr/Re2 ). Evaporation rate from wavy water surface is strongly affected by combinations between wave steepness and main airflow velocity above the wavy water surface. Experimental results show that no pattern can be followed for which combinations of evaporation rate will increase. Thus, only two facts can be noticed: the evaporation rate is larger than that measured under the same airflow velocity conditions with no waves existing on evaporated water surface because the airflow is smooth and attached along the still water surface and when increasing the wave steepness(H/L,H/T), Airflow will separate at the lee side of wave crest near to the bottom of the wave trough. Thus, vortex will generate in the airflow separation region. These vortexes are unstable and cause an increase in turbulence, reducing the water surface's resistance to vertical transport water vapor and increasing the evaporation rate. Also, experimental results show that the evaporation rates are somewhat less than that measured under the same airflow velocity with smaller wave steepness due to air trapped region observed at the leeside of the wave crest near the bottom of the wave trough. Evaporation rate is increasing with increase airflow velocity under the same convection regime.

Multistage Impinging Stream Drying for Okara

2017 ◽  
Vol 33 (4) ◽  
pp. 445-450 ◽  
Author(s):  
Chatchai Nimmol ◽  
Anucha Hirunwat
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Feed Rate ◽  
Evaporation Rate ◽  
Specific Energy Consumption ◽  
Water Evaporation ◽  
Two Stage ◽  
Drying Temperature ◽  
One Stage

Abstract. In this study, a multistage drying concept (one-stage and two-stage drying) was applied in an attempt to enhance the performance and energy efficiency of an impinging stream dryer for okara, which is a soy residue obtained from soymilk production. The volumetric water evaporation rate, the volumetric heat transfer coefficient and the specific energy consumption of the drying system at various drying conditions were evaluated. For one-stage drying, the volumetric water evaporation rate increased with an increase in the okara feed rate and the drying temperature. The effect of the drying temperature was insignificant at the minimum okara feed rate, however. For two-stage drying, the drying temperature insignificantly affected the volumetric water evaporation rate. However, an increase in the okara feed rate led to an increase in the volumetric water evaporation rate. The effects of the drying temperature and the okara feed rate on the volumetric heat transfer coefficient were similar to those of the volumetric water evaporation rate, for both one-stage and two-stage drying. The maximum volumetric water evaporation rate and the maximum volumetric heat transfer coefficient of 1784 kgwater m-3 h-1 and 3385 W m-3 K-1, respectively, were noted during one-stage drying at the drying temperature of 150°C and the okara feed rate of 45 kgdrysolid h-1. Regarding the energy efficiency of the drying process expressed in terms of the specific energy consumption (SEC), an increase in the drying temperature and the okara feed rate led to lower values of the SEC for one-stage drying. The effect of the okara feed rate on the SEC for two-stage drying was similar to that for one-stage drying. However, the opposite trend was observed for the effect of the drying temperature. When a multistage drying concept was applied to the impinging stream dryer, the percentage of moisture content reduction of the okara were substantially decreased. The results obtained from this study implied that an impinging stream dryer with a multistage drying concept may be used to dry okara or other high-moisture particulate materials. Keywords: Impinging stream dryer, Multistage drying, Okara, Specific energy consumption, Volumetric heat transfer coefficient, Volumetric water evaporation rate.

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