Determination of average temperature difference during vapor condensation on liquid jets

1983 ◽  
Vol 19 (8) ◽  
pp. 332-334 ◽  
Author(s):  
L. I. Trofimov
Keyword(s):  
Temperature Difference ◽  
Vapor Condensation ◽  
Liquid Jets ◽  
Average Temperature ◽  
Average Temperature Difference

Experimental Investigation of Lab-Scale, Heat Exchanger Prototypes Designed to Provide Refugia for Trout

2021 ◽  
Author(s):  
Rajib Uddin Rony ◽  
Adam Gladen ◽  
Sarah LaVallie ◽  
Jeremy Kientz
Keyword(s):  
Heat Exchanger ◽  
Temperature Difference ◽  
Large Scale ◽  
Cold Water ◽  
Cooling System ◽  
Tube Bundle ◽  
Small Scale ◽  
Scaled Model ◽  
Average Temperature ◽  
Average Temperature Difference

Abstract In recent years Spring Creek in South Dakota, a popular fishing location, has been experiencing higher surface water temperatures, which negatively impact cold-water trout species. One potential solution is to provide localized refugia of colder water produced via active cooling. The present work focuses on the design and testing of a small-scale prototype heat exchanger, for such a cooling system. Various prototypes of the heat exchanger were tested in a 1/10th-scaled model of a section of the creek. A staggered, tube-bundle heat exchanger was used. The prototypes consisted of just the heat exchanger placed directly in the scaled-stream model and of the heat exchanger placed inside an enclosure with an aperture. The results show that, without the enclosure, the average temperature difference is 0.64 °C, with a corresponding heat transfer requirement of 1.63 kW/°C of cooling. However, with an enclosure, the average temperature difference is 1.95 °C, which required 0.59 kW/°C of cooling. Modifications to the enclosure decrease the average temperature difference but also decrease the standard deviation of the temperature difference. Thus, the cooling effect is more evenly spread throughout the water in the enclosure. This indicates that the enclosure design can be used to balance the requirements of obtaining a desired temperature difference with a relatively low spatial variation in that temperature difference. These results will be used to guide the design of the large-scale heat exchanger prototype.

scholarly journals Selection and Evaluation of influencing Parameters for Heat Load Forecasting Model

2021 ◽  
Vol 252 ◽  
pp. 03027
Author(s):  
Yuli Wu ◽  
Rui Li
Keyword(s):  
Prediction Model ◽  
Temperature Difference ◽  
Hot Water ◽  
Outdoor Temperature ◽  
Domestic Hot Water ◽  
Model Input ◽  
Average Temperature ◽  
Average Temperature Difference ◽  
Input Parameters ◽  
Heating Load

This paper analyses the factors affecting the heating consumption of a heating substation. The input parameters of neural network prediction model are analysed and selected. The average absolute error, average absolute percentage error, and mean square error are used to evaluate the effect of the prediction model. The results show that when the model input parameters are the maximum outdoor temperature, the average outdoor temperature, the average temperature difference between the primary supply and return of domestic hot water, the heating load in the previous three days, the heating load in the previous two days, the heating load in the previous day and when the model input parameters are the maximum outdoor temperature, the minimum outdoor temperature, the average outdoor temperature, the average temperature difference between the primary supply and return of domestic hot water, the heating load of the previous three days, the heating load of the previous two days, the heating load of the previous day, the effects are better.

scholarly journals Field Study on the Microclimate of Public Spaces in Traditional Residential Areas in a Severe Cold Region of China

2019 ◽  
Vol 16 (16) ◽  
pp. 2986 ◽  
Author(s):  
Yujie Lin ◽  
Yumeng Jin ◽  
Hong Jin
Keyword(s):  
Wind Speed ◽  
Temperature Difference ◽  
Public Spaces ◽  
Average Wind Speed ◽  
Coverage Ratio ◽  
Wind Speeds ◽  
Average Temperature ◽  
Average Temperature Difference ◽  
Average Wind ◽  
The Difference

As residential environment science advances, the environmental quality of outdoor microclimates has aroused increasing attention of scholars majoring in urban climate and built environments. Taking the microclimate of a traditional residential area in a severe cold city as the study object, this study explored the influence of spatial geometry factors on the microclimate of streets and courtyards by field measurements, then compared the differences in microclimate of distinct public spaces. The results are as follows. (1) The temperature of a NE-SW (Northeast-Southwest) oriented street was higher than that of a NW-SE (Northwest-Southeast) oriented street in both summer and winter, with an average temperature difference of 0.7–1.4 °C. The wind speeds in the latter street were slower, and the difference in average wind speed was 0.2 m/s. (2) In the street with a higher green coverage ratio, the temperature was much lower, a difference that was more obvious in summer. The difference in mean temperature was up to 1.2 °C. The difference in wind speed between the two streets was not obvious in winter, whereas the wind speed in summer was significantly lower for the street with a higher green coverage ratio, and the difference in average wind speed was 0.7 m/s. (3) The courtyards with higher SVF (sky view factor) had higher wind speeds in winter and summer, and the courtyards with larger SVF values had higher temperatures in summer, with an average temperature difference of 0.4 °C. (4) When the spaces had the same SVF values and green coverage ratios, the temperature of the street and courtyard were very similar, in both winter and summer. The wind speed of the street was significantly higher than the courtyard in summer, and the wind speed difference was 0.4 m/s.

THE COEFFICIENT OF HEAT TRANSFER FOR VERTICAL SURFACES IN STILL AIR

1937 ◽  
Vol 15a (7) ◽  
pp. 109-117
Author(s):  
R. Ruedy
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Heat Loss ◽  
Temperature Difference ◽  
Plane Surface ◽  
Vertical Plane ◽  
Black Body ◽  
Average Temperature ◽  
Fourth Root

For a vertical plane surface in still air the coefficient of heat transfer, valid within the range of temperatures occurring in buildings, depends on the temperature and the height of the surface. If black body conditions are assumed for the heat lost by radiation, the coefficient is equal to 1.39, 1.50, 1.62, and 1.73 B.t.u. per sq. ft. per ° F. at 32°, 50°, 68°, and 86° F. respectively, the height of the heated surfaces being 100 cm. Convection is responsible for about one-third, and radiation, mainly in the region of 10 microns, for about two-thirds of the heat loss. Convection currents depend on the temperature difference, while radiation depends on the average temperature. When attempts are made to stop convection currents by placing obstacles across the surface, the loss of heat due to natural convection varies inversely as the fourth root of the height, providing that the nature of the flow of air remains unchanged.

scholarly journals Thermo-voltage measurements of atomic contacts at low temperature

2016 ◽  
Vol 7 ◽  
pp. 767-775 ◽  
Author(s):  
Ayelet Ofarim ◽  
Bastian Kopp ◽  
Thomas Möller ◽  
León Martin ◽  
Johannes Boneberg ◽  
...  
Keyword(s):  
Finite Element ◽  
Low Temperature ◽  
Temperature Difference ◽  
Laser Heating ◽  
Laser Source ◽  
Break Junction ◽  
Resistance Change ◽  
Element Simulation ◽  
Novel Method

We report the development of a novel method to determine the thermopower of atomic-sized gold contacts at low temperature. For these measurements a mechanically controllable break junction (MCBJ) system is used and a laser source generates a temperature difference of a few kelvins across the junction to create a thermo-voltage. Since the temperature difference enters directly into the Seebeck coefficient S = −ΔV/ΔT, the determination of the temperature plays an important role. We present a method for the determination of the temperature difference using a combination of a finite element simulation, which reveals the temperature distribution of the sample, and the measurement of the resistance change due to laser heating of sensor leads on both sides next to the junction. Our results for the measured thermopower are in agreement with recent reports in the literature.

A thermal method for the determination of tissue blood flow

1975 ◽  
Vol 39 (1) ◽  
pp. 170-173 ◽  
Author(s):  
T. V. McCaffrey ◽  
R. D. McCook
Keyword(s):  
Thermal Conductivity ◽  
Blood Flow ◽  
Integrated Circuits ◽  
Myocardial Blood Flow ◽  
Temperature Difference ◽  
Tissue Blood Flow ◽  
Thermal Method ◽  
Fixed Temperature ◽  
Voltage Output

An isothermal flowmeter for the determination of local tissue blood flow is described. Flow is determined by the measurement of the thermal conductivity of the tissue in the vicinity of a heated thermistor maintained at a fixed temperature difference above a reference thermistor. Direct heating of the thermistor is utilized to eliminate the need for specially constructed indirectly heated thermistors. This design results in a device with a voltage output directly proportional to tissue thermal conductivity and to tissue blood flow. The device is shown to be adequate for the qualitative measurement of myocardial blood flow under various situations. Construction is simplified and the size of the circuit reduced by the use of readily available integrated circuits.

The Influence of Hydrodynamic Bearing Configuration on Morton Effect

2016 ◽  
Author(s):  
Xiaomeng Tong ◽  
Alan Palazzolo
Keyword(s):  
Temperature Distribution ◽  
Film Thickness ◽  
Temperature Difference ◽  
Thermal Excitation ◽  
Vibration Level ◽  
Critical Speeds ◽  
Average Temperature ◽  
Bearing Clearance ◽  
Comparison Results ◽  
Morton Effect

The Morton effect (ME) results from the synchronous, thermal excitation of a rotating shaft because of the uneven viscous shearing in hydrodynamic bearings and the asymmetric temperature distribution in shafts. The temperature difference bends the rotor, reducing the film thickness and increasing the thermal unbalance, which may cause excessive vibration level and unsteady phase angle. To predict the potential thermal instability from the ME, the finite element method is used to solve the transient rotordynamics and temperature distribution in the lubricant, bearing and shaft. The conventional thermal unbalance method is replaced by a more accurate thermal shaft bow model for rotordynamic analysis and the three-dimensional energy equation is utilized for the lubricant temperature prediction. Considering that the temperature change in the shaft and bearing occurs quite slowly relative to the shaft vibration deflection change, a staggered scheme is employed to assign a longer period to update the system temperature distribution and a shorter period to update the vibration orbits. Verified by a real overhung compressor model, the ME instability onset speed predicted by simulation coincides with the tested speed, at which large vibration level is observed. The hysteresis phenomenon, which is quite typical for thermal-induced vibration problems, can be caused by the ME and is demonstrated by the simulation. A stability recovery speed is confirmed, above which the vibration level and the rotor temperature difference will decrease to an acceptable level and the system will become stable. To investigate the influence of bearing configuration on ME, different bearing types including fixed pad bearings (FPBs) and tilting pad bearings (TPBs) with various pad numbers are analyzed. Meanwhile, the bearing clearance and preload intentionally remain unchanged in the comparison. Results show that despite similar critical speeds, the TPBs are better at suppressing the ME with lower average temperature and larger film thickness in the lubricant, especially at high speeds. This is due to the self-tilting ability for the TPBs to maintain a satisfactory bearing clearance. The four-pad TPBs outperform the five-pad TPBs with both lower average temperature and smaller temperature difference in the shaft considering that the effective load-carrying area is larger in the 4-pad bearings. Moreover, the asymmetric pivot offset of 0.6 is simulated to demonstrate its superiority in mitigating the ME compared with the common 0.5 offset. Considering that the ME instability occurs in the vicinity of the critical speeds in most cases, the bearing diameter-length ratio should be carefully designed to achieve a larger separation margin.

Study on the Influence of Neighbour Room Heat Transfer on the Indoor Thermal Environment in a Heating Room

2014 ◽  
Vol 1070-1072 ◽  
pp. 2006-2009
Author(s):  
Ye Wang ◽  
Tong Zou ◽  
Wen Ting Hu
Keyword(s):  
Heat Transfer ◽  
Temperature Difference ◽  
Thermal Environment ◽  
Internal Surface ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Indoor Thermal Environment ◽  
Average Temperature ◽  
Nusselt Numbers ◽  
Temperature Filed

To obtain the influence of the neighbour room heat transfer on the radiator heat transfer characteristics and indoor thermal environment, a new k-ε model is used to numerically simulate the radiator surface heat transfer ability, indoor velocity field and temperature filed at different neighbour room heat transfer temperature differences. The results indicate that both the radiator surface temperature and the average Nusselt numbers on radiator surface are approximately increasing with the increasing neighbour room heat transfer temperature differences when the indoor average temperature is up to 18°C. At the same neighbour room heat transfer temperature difference, the local heat transfer ability is decreasing gradually from the bottom to the top of the radiator surface. The temperature gradient close to the floor is decreasing with the increasing neighbour room heat transfer temperature difference and the indoor temperature is tending to be more homogeneous. And the velocity gradients close to the ceiling and the internal surface of east wall are higher for the case that the neighbour room heat transfer is considered.

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