Mean Temperature Difference in Multipass Crossflow

1983 ◽  
Vol 105 (3) ◽  
pp. 584-591 ◽  
Author(s):  
A. Pignotti ◽  
G. O. Cordero
Keyword(s):  
Temperature Difference ◽  
Heat Exchangers ◽  
Arbitrary Number ◽  
Mean Temperature ◽  
Air Mixing ◽  
The Mean ◽  
Number Of Passes ◽  
Analytical Expressions

A procedure is developed to obtain analytical expressions for the mean temperature difference in crossflow heat exchangers with arbitrary number of passes and rows per pass. The influence of air mixing, along with different flow arrangements for the tube fluid between passes, is analyzed, both in co- and counter-crossflow.

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.

Calculation of Mean Temperature Difference in Air-Cooled Cross-Flow Heat Exchangers

1979 ◽  
Vol 101 (3) ◽  
pp. 511-513 ◽  
Author(s):  
W. Roetzel ◽  
J. Neubert
Keyword(s):  
Temperature Difference ◽  
Heat Exchangers ◽  
Cross Flow ◽  
Process Stream ◽  
Explicit Equation ◽  
Fast Calculation ◽  
Mean Temperature ◽  
Flow Heat ◽  
The Mean ◽  
Empirical Coefficients

An approximate explicit equation together with empirical coefficients is presented for the fast calculation of the mean temperature difference of eight cross-flow arrangements. The mean temperature difference is calculated from the effectiveness of the process stream and the number of transfer units on the air side.

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 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.

scholarly journals Air exchange through doorways. The effect of temperature difference, turbulence and ventilation flow

1977 ◽  
Vol 79 (1) ◽  
pp. 141-154 ◽  
Author(s):  
O. M. Lidwell
Keyword(s):  
Theoretical Model ◽  
Temperature Difference ◽  
Effect Of Temperature ◽  
Air Mass ◽  
Excess Air ◽  
Outflow Velocity ◽  
Simple Theoretical Model ◽  
Air Supply ◽  
Air Mixing ◽  
Analytical Expressions

SUMMARYAnalytical expressions have been derived for the exchange of air across doorways or similar apertures, in terms of the temperature difference between the spaces on both sides of the opening and the net volume of air flowing through this as a result of unbalanced air supply or extract. A simple allowance for turbulence which gives reasonable correspondence with observation is included. The formulae, which assume complete air mixing on both sides of the doorway up to the plane of the aperture, predict outflows from the warmer side, when there is an excess air supply to this side, which are progressively smaller than those observed as the temperature difference rises above 2–3 °C and the volume of excess air supply increases to produce an averaged outflow velocity greater than 0·1–0·15m/s. This seems to be due to lack of mixing of the warm outflowing air with the cooler air mass. A correction factor for this can be deduced as a function of the pressure difference due to the excess air supply. The limiting magnitude and general form of this function are compatible with a simple theoretical model of the air flow patterns involved.

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