Mean Temperature Difference Charts for Air Coolers

1983 ◽  
Vol 105 (3) ◽  
pp. 592-597 ◽  
Author(s):  
A. Pignotti ◽  
G. O. Cordero
Keyword(s):  
Heat Transfer ◽  
Heat Capacity ◽  
Temperature Difference ◽  
Optimization Technique ◽  
Independent Variables ◽  
Mean Temperature ◽  
Air Cooler ◽  
The Mean ◽  
The One ◽  
Water Ratio

Computer generated graphs are presented for the mean temperature difference in typical air cooler configurations, covering the combinations of numbers of passes and rows per pass of industrial interest. Two sets of independent variables are included in the graphs: the conventional one (heat capacity water ratio and cold fluid effectiveness), and the one required in an optimization technique of widespread use (hot fluid effectiveness and the number of heat transfer units). Flow arrangements with side-by-side and over-and-under passes, frequently found in actual practice, are discussed through examples.

scholarly journals The Recuperative Heat Exchangers – The Mean Temperature Difference in the Special Cases of Heat Transfer

2020 ◽  
Vol 70 (1) ◽  
pp. 47-56
Author(s):  
Gužela Štefan ◽  
Dzianik František
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Temperature Difference ◽  
Heat Exchangers ◽  
Operating Characteristic ◽  
Mean Temperature ◽  
Special Cases ◽  
Key Variables ◽  
The Mean

AbstractThe heat exchangers are used to heat or cool the material streams. To calculate the heat exchanger, it is important to know the type of heat exchanger and its operating characteristic. This characteristic determines one of the key variables (e.g., F, NTUmin, or θ). In some special cases, it is not necessary to know its operating characteristic to calculate the heat exchanger. This article deals with these special cases. The article also contains a general dependency that allows checking the key variables related to a given heat exchanger.

The Effect of Temperature Modulation on Natural Convection in a Horizontal Layer Heated From Below: High-Rayleigh-Number Experiments

1994 ◽  
Vol 116 (3) ◽  
pp. 614-620 ◽  
Author(s):  
J. Mantle ◽  
M. Kazmierczak ◽  
B. Hiawy
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Rayleigh Number ◽  
Temperature Difference ◽  
Wall Temperature ◽  
Bottom Wall ◽  
Large Temperature ◽  
Temperature Modulation ◽  
Mean Temperature ◽  
The Mean

An experimental investigation was conducted to study the effects of wall temperature modulation in a horizontal fluid layer heated from below. A series of 45 transient experiments was performed in which the bottom wall temperature changed periodically with time in a “sawtoothlike” fashion. The amplitude of the bottom wall temperature oscillation varied from 3 to 70 percent of the enclosure’s mean temperature difference, and the period of the temperature swings ranged from 43 seconds to 93 minutes. With water as the fluid in the test cell, the flow was fully turbulent at all times. The Rayleigh number of the experiments (based on the enclosure’s height and on the mean temperature difference) was 0.4 × 108 < Ra < 1.2 × 109. It was found that for small changes in the bottom wall temperature, the cycle-averaged heat transfer through the layer was unchanged, independent of the period, and was equal in magnitude to the well-established steady-state value when the hot wall is evaluated at the mean temperature. However, this study shows that the cycle-averaged heat transfer increases notably, up to 12 percent as compared to the steady-state value, for the experiments with large temperature modulations. Futhermore, it was observed that the enchancement was a function of the amplitude and period of the oscillation.

scholarly journals VI.—The Body-Temperature of Fishes and other Marine Animals.

1908 ◽  
Vol 28 ◽  
pp. 66-84 ◽  
Author(s):  
Sutherland Simpson
Keyword(s):  
Body Temperature ◽  
Temperature Difference ◽  
Great Majority ◽  
The Body ◽  
Shore Crab ◽  
First Year ◽  
Marine Animals ◽  
Mean Temperature ◽  
The Mean ◽  
Image Position

SUMMARYThe body-temperature of the following fishes, crustaceans, and echinoderms has been examined and compared with the temperature of the water in which they live:—Cod-fish (Gadus morrhua), ling (Molva vulgaris), torsk (Brosmius brosme), coal-fish or saithe (Gadus virens), haddock (Gadus œgelfinus), flounder (Pleuronectes flesus), smelt (Osmerus eperlanus), dog-fish (Scyllium catulus), shore crab (Carcinus mœnas), edible crab (Cancer pagurus), lobster (Homarus vulgaris), sea-urchin (Echinus esculentus), and starfish (Asterias rubens). The minimum, maximum, and mean temperature difference for each species are given in the following table:—The excess of temperature is most evident in the larger specimens. This is well shown in the case of the coal-fish, where in the adult it was 0°·7 C., and in the great majority (11 out of 12) of the young of the first year, 0°·0 C. The body-weight and the conditions under which the fish are captured probably form the most important factors in determining the temperature difference.In 14 codfish, where the rectal, blood, and muscle temperatures were recorded in the same individual, it was found to be highest in the muscle and lowest in the rectum, the mean temperature difference being 0°·46 C. for the muscle, 0°·41 C for the blood, and 0°·36 C. for the rectum.

scholarly journals Effectiveness of Tympanic Thermometry for diagnosing Acute Otitis Media

2019 ◽  
Vol 8 (2) ◽  
pp. 74-78
Author(s):  
Muhammad Zubair ◽  
Ghulam Saqulain ◽  
Arfat Jawaid
Keyword(s):  
Tympanic Membrane ◽  
Otitis Media ◽  
Temperature Difference ◽  
Acute Otitis Media ◽  
P Value ◽  
Upper Respiratory Tract ◽  
Mean Temperature ◽  
Ear Wax ◽  
The Mean ◽  
Group B

Background: Acute Otitis Media (AOM) is a common upper respiratory tract infection (URTI) in children and usually presents with fever and otalgia. AOM is characterized by congested tympanic membrane and possible increase in temperature, which might be picked up by infrared tympanic thermometry. The objective of this study was to compare the temperature difference of tympanic membrane of affected ear with the unaffected ear and axilla in unilateral acute otitis media, and compare it with the control group.Material and Methods: This case control study comprised of 200 cases of both genders, aged up to 5 years. They were divided into two groups; Group A included 100 clinically diagnosed cases of acute otitis media (AOM), who reported in the ENT Outpatient Department (OPD) and Group B included 100 controls who presented in General Filter Clinic with no ear complaints. Cases with chronic ear disease, ear discharge, and use of local drugs including ear drops, impacted ear wax, tragal tenderness and congenital malformations of the ear were excluded by taking a detailed history. Clinical examination including otoscopy by an expert was done before subjecting patients to axillary and tympanic thermometry measurements and data recording. Data was collected and tabulated using Microsoft Excel Worksheet and analyzed by SPSS 16. Qualitative data like gender were presented as percentage and ratio, while means and standard deviation were calculated for the quantitative data. Difference between the means of experimental and control groups were analyzed by independent sample t-test and P value of less than or equal to 0.05 was taken as significant.Results: This study included 100 cases of unilateral AOM and 100 normal controls without AOM. In patients with AOM, the mean temperature difference between the affected ear and axilla was 1.41ºF as compared to 0.075ºF in controls (p=0.026). While the mean temperature difference between the affected ear and other ear was 0.65ºF as compared to 0.19ºF in controls (p=0.069).Conclusion: In acute otitis media, the temperature of affected ear is significantly higher than axilla but was not significantly higher than the other ear. The finding may help establish thermometry as a diagnostic tool in clinics manned by doctors not competent to do otoscopy.

Analysis of Turbulent Thermal Convection Between Horizontal Plates

1983 ◽  
Vol 105 (4) ◽  
pp. 789-794 ◽  
Author(s):  
M. Kaviany ◽  
R. Seban
Keyword(s):  
Temperature Distribution ◽  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
Thermal Convection ◽  
Equation Model ◽  
Experimental Results ◽  
Mixing Length ◽  
Mean Temperature ◽  
The Mean ◽  
The One

The one-equation model of turbulence is applied to the turbulent thermal convection between horizontal plates maintained at constant temperatures. A pseudo-three-layer model is used consisting of a conduction sublayer adjacent to the plates, a turbulent region within which the mixing length increases linearly, and a turbulent core within which the mixing length is a constant. It is assumed that the Nusselt number varies with the Rayleigh number to the one-third power. As a result, the steady-state distributions of the turbulent kinetic energy and the mean temperature are obtrained and presented in closed forms. These results include the effects of Prandtl number. The predictions are compared with the available experimental results for different Prandtl and Rayleigh numbers. Also included are the predictions of Kraichnan, which are based on a less exact analysis. The results of the one-equation model are in fair agreement with the experimental results for the distribution of the turbulent kinetic energy and the mean temperature distribution. The predictions of Kraichnan are in better agreement with the experimental results for the mean temperature distribution.

Mean Temperature Difference for Heat Exchanger Design—A General Approximate Explicit Equation

1975 ◽  
Vol 97 (1) ◽  
pp. 5-8 ◽  
Author(s):  
W. Roetzel ◽  
F. J. L. Nicole
Keyword(s):  
Temperature Difference ◽  
Cross Flow ◽  
Approximate Equation ◽  
Explicit Equation ◽  
Fast Calculation ◽  
Heat Exchanger Design ◽  
Mean Temperature ◽  
Shell And Tube ◽  
The Mean ◽  
Empirical Coefficients

An approximate equation together with empirical coefficients is presented for the fast calculation of the mean temperature difference of nine countercurrent cross-flow arrangements, as applied in air-cooled heat exchangers. The same equation can be used for other flow systems, as demonstrated for one shell-and-tube arrangement.

scholarly journals Tables of the variation, through a cycle of nine years, of the mean height of the barometer, mean temperature, and depth of rain, as connected with the prevailing winds, influenced in their direction by the occurrence of the lunar apsides, with some concluding observations on the result

1843 ◽  
Vol 4 ◽  
pp. 226-227
Keyword(s):  
The Other ◽  
Mean Temperature ◽  
The Mean ◽  
The One

From the Tables here given, the author draws the following conclusions:— 1 The barometer is higher under the lunar apogee, than under the perigee; the mean height in the former case being 29·84517, and in the latter, 29·75542. 2. The mean temperature is lower under the apogee than under the perigee; that of the former being 48°·7126, and of the latter, 49°·0356. The mean of the whole year was 48°·7126. 3. The rain of the weeks following the apsis exceeds that under the perigee; but with two striking exceptions in the annual result of nine years, the one in the wettest, and the other in the driest year of the cycle.

EFFET DU CLIMAT SUR LA FLETRISSURE BACTERIENNE DE LA POMME DE TERRE ET RELATION AVEC LE CONTENU EN SUCRES DES TIGES

1976 ◽  
Vol 56 (3) ◽  
pp. 549-554 ◽  
Author(s):  
ROGER PAQUIN ◽  
H. GÉNÉREUX
Keyword(s):  
Sugar Content ◽  
Degree Days ◽  
Bacterial Ring Rot ◽  
Higher Plant ◽  
Disease Evolution ◽  
Ring Rot ◽  
Mean Temperature ◽  
Northern Regions ◽  
The Mean ◽  
The One

Potato cultivars resistant to bacterial ring rot, inoculated with Corynebacterium sepedonicum, were more infected in the northern regions (North Shore) than at La Pocatière (South Shore of St. Lawrence River) where the number of degree-days and mean temperatures are higher. Plant stems from the Northern regions had a higher total and reducing sugar content than those of La Pocatière and there was a significant correlation between sugar content and the mean temperature or the number of degree-days. However, the latter correlation is more significant than the one between the percentage of infected plants and the mean temperature or the number of degree-days in that region. The possible role of sugars in the disease evolution in the cool regions is discussed.

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