scholarly journals A Comprehensive Mathematical Model for Simulation of Latent and Sensible Heat Losses from Wet-Skin Surface and Fur Layer of a Cow

2010 ◽  
Vol 7 (1) ◽  
pp. 83-96
Author(s):  
Z.A. Khan ◽  
I.A. Badruddin ◽  
M. Mokhtar ◽  
W.M.W. Muahamad
Keyword(s):  
Mathematical Model ◽  
Relative Humidity ◽  
Heat Loss ◽  
Ambient Air ◽  
Skin Surface ◽  
Heat Losses ◽  
Air Velocity ◽  
Hot Environment ◽  
Total Body ◽  
Body Heat

This paper presents a comprehensive mathematical model that calculates heat and mass transfer from the skin surface and fur layer of a cow. The model predicts evaporative, respiratory, convective, radiant and urine heat losses for different levels of skin and fur wetness, air velocity, ambient temperature, relative humidity, breathing rate and volume of urine discharged per unit time. Effect of various environmental conditions on skin temperature and consequently heat loss from cow’s body is discussed. It is found that the heat loss through respiration is significant and can not be ignored. Evaporative cooling and respiratory heat losses are, decreased due to increased relative humidity because of increased saturation of ambient air with water particles. It is also found that very small proportion of total body heat is lost through urine in stressful hot environment.

Drying of Heavily Salted Fish

1945 ◽  
Vol 6d (5) ◽  
pp. 380-391 ◽  
Author(s):  
E. P. Linton ◽  
A. L. Wood
Keyword(s):  
Relative Humidity ◽  
Air Temperature ◽  
Skin Surface ◽  
Medium Size ◽  
Air Velocity ◽  
Salted Fish

The experimental drying of cut samples and of whole salt fish under various air conditions shows that the optimum air velocity is 100 to 125 cm. per second, air temperature 26 °C, and relative humidity 45 to 55 per cent. High drying potentials inhibit drying owing to the formation of an impervious salt-protein crust on the surface of the fish.The skin surface of the fish dries about 50 to 75 per cent as fast as the split surface. Under the recommended air conditions medium size salt codfish are dried from 130 per cent to 75 per cent, dry basis, moisture in about 40 hours.

Quantifying the cooling efficiency of air velocity by heat loss from skin surface in warm and hot environments

2018 ◽  
Vol 136 ◽  
pp. 146-155 ◽  
Author(s):  
Chenqiu Du ◽  
Baizhan Li ◽  
Hong Liu ◽  
Yifan Wei ◽  
Meilan Tan
Keyword(s):  
Heat Loss ◽  
Skin Surface ◽  
Cooling Efficiency ◽  
Air Velocity ◽  
Hot Environments

Effects of Dry Chilling on the Microflora on Beef Carcasses at a Canadian Beef Packing Plant

2016 ◽  
Vol 79 (4) ◽  
pp. 538-543 ◽  
Author(s):  
Y. LIU ◽  
M. K. YOUSSEF ◽  
X. YANG
Keyword(s):  
Escherichia Coli ◽  
Relative Humidity ◽  
Air Temperature ◽  
Ambient Air ◽  
Indicator Organisms ◽  
Air Velocity ◽  
E Coli ◽  
Beef Carcasses ◽  
Significant Difference

ABSTRACT The aim of this study was to determine the course of effects on the microflora on beef carcasses of a commercial dry chilling process in which carcasses were dry chilled for 3 days. Groups of 25 carcasses selected at random were sampled when the chilling process commenced and after the carcasses were chilled for 1, 2, 4, 6, 8, 24, and 67 h for determination of the numbers of aerobes, coliforms, and Escherichia coli. The temperatures of the surfaces and the thickest part of the hip (deep leg) of carcasses, as well as the ambient air conditions, including air temperature, velocity, and relative humidity (RH), were monitored throughout the chilling process. The chiller was operated at 0°C with an off-coil RH of 88%. The air velocity was 1.65 m/s when the chiller was loaded. The initial RH levels of the air in the vicinity of carcasses varied with the locations of carcasses in the chiller and decreased rapidly during the first hour of chilling. The average times for shoulder surfaces, rump surfaces, and the deep leg of carcasses to reach 7°C were 13.6 ± 3.1, 16.0 ± 2.4 and 32.4 ± 3.2 h, respectively. The numbers of aerobes, coliforms, and E. coli on carcasses before chilling were 5.33 ± 0.42, 1.95 ± 0.77, 1.42 ± 0.78 log CFU/4,000 cm2, respectively. The number of aerobes on carcasses was reduced by 1 log unit each in the first hour of chilling and in the subsequent 23 h of chilling. There was no significant difference (P > 0.05) between the numbers of aerobes recovered from carcasses after 24 and 67 h of chilling. The total numbers (log CFU/100,000 cm2) on carcasses before chilling and after the first hour of chilling were 3.86 and 2.24 for coliforms and 3.30 and 2.04 for E. coli. The subsequent 23 h of chilling reduced the numbers of both groups of organisms by a further log unit. No coliforms or E. coli were recovered after 67 h of chilling. The findings show that the chilling regime investigated in this study resulted in significant reductions of all three groups of indicator organisms.

Air velocity influences thermoregulation and endurance exercise capacity in the heat

2018 ◽  
Vol 43 (2) ◽  
pp. 131-138 ◽  
Author(s):  
Hidenori Otani ◽  
Mitsuharu Kaya ◽  
Akira Tamaki ◽  
Phillip Watson ◽  
Ronald J. Maughan
Keyword(s):  
Skin Temperature ◽  
Heat Loss ◽  
Exercise Capacity ◽  
Core Temperature ◽  
Endurance Exercise ◽  
Temperature Rise ◽  
Time To Exhaustion ◽  
Evaporative Heat Loss ◽  
Air Velocity ◽  
Hot Environment

This study examined the effects of variations in air velocity on time to exhaustion and thermoregulatory and perceptual responses to exercise in a hot environment. Eight male volunteers completed stationary cycle exercise trials at 70% peak oxygen uptake until exhaustion in an environmental chamber maintained at 30 °C and 50% relative humidity. Four air velocity conditions, 30, 20, 10, and 0 km/h, were tested, and the headwind was directed at the frontal aspect of the subject by 2 industrial fans, with blade diameters of 1 m and 0.5 m, set in series and positioned 3 m from the subject’s chest. Mean ± SD time to exhaustion was 90 ± 17, 73 ± 16, 58 ± 13, and 41 ± 10 min in 30-, 20-, 10-, and 0-km/h trials, respectively, and was different between all trials (P < 0.05). There were progressive elevations in the rate of core temperature rise, mean skin temperature, and perceived thermal sensation as airflow decreases (P < 0.05). Core temperature, heart rate, cutaneous vascular conductance, and perceived exertion were higher and evaporative heat loss was lower without airflow than at any given airflow (P < 0.05). Dry heat loss and plasma volume were similar between trials (P > 0.05). The present study demonstrated a progressive reduction in time to exhaustion as air velocity decreases. This response is associated with a faster rate of core temperature rise and a higher skin temperature and perceived thermal stress with decreasing airflow. Moreover, airflow greater than 10 km/h (2.8 m/s) might contribute to enhancing endurance exercise capacity and reducing thermoregulatory, cardiovascular, and perceptual strain during exercise in a hot environment.

scholarly journals Effect of relative humidity on heat transfer across the surface of an evaporating water droplet in air flow

2009 ◽  
Vol 624 ◽  
pp. 57-67 ◽  
Author(s):  
RYOICHI KUROSE ◽  
AKITOSHI FUJITA ◽  
SATORU KOMORI
Keyword(s):  
Heat Transfer ◽  
Relative Humidity ◽  
Heat Loss ◽  
Water Droplet ◽  
Rear Surface ◽  
Ambient Air ◽  
Droplet Surface ◽  
Droplet Temperature ◽  
Humidity Condition ◽  
Evaporation Heat

A three-dimensional direct numerical simulation (DNS) is applied to flows inside and outside an evaporating spherical water droplet in air, and the effect of relative humidity on the heat transfer between the droplet and ambient air is investigated. The initial air temperature is set to be 15 K higher than the initial droplet temperature. The results show that the local evaporation heat loss indicates the maximum on the front of the droplet and decreases on going from the front to the rear, and the reduction on the rear becomes marked for high-droplet Reynolds numbers. This is because the evaporation rate is suppressed on the rear surface by the presence of flow separations behind the droplet. The droplet temperature decreases in the low-humidity condition, whereas it increases in the high-humidity condition. This difference is caused by the heat balance of evaporation heat loss and convective heat gain from ambient air at the droplet surface.

The cooling effect of a spray fan in an indoor hot environment

2020 ◽  
pp. 1420326X2091436
Author(s):  
Xiaojing Meng ◽  
Yihang Lv ◽  
Honggang Yang ◽  
Yi Wang
Keyword(s):  
Relative Humidity ◽  
Thermal Environment ◽  
Cooling Effect ◽  
Air Velocity ◽  
Velocity Increase ◽  
Wet Bulb Globe Temperature ◽  
Hot Environment ◽  
Globe Temperature ◽  
Set Up ◽  
Black Globe Temperature

The aim of this study is to evaluate the cooling effect of a spray fan in an indoor hot environment. An experimental workplace with a thermal environment of high temperature and radiation intensity was set up. The hot environment of the experimental workplace could not meet occupational health requirements when the heat source temperature exceeded 150°C. The effects of air velocity and relative humidity on the natural wet bulb temperature, black globe temperature and wet bulb globe temperature (WBGT) were investigated. The maximum reduction of the WBGT was about 1.7°C, with an air velocity increase by 1 m/s. There was a notable cooling effect on the hot environment for low air velocities (e.g. 0–2 m/s), while the cooling effect only increased slightly for high air velocity (e.g. 2–5 m/s). We also found that the indoor WBGT declined by 0.2–0.8°C when the relative humidity was increased by about 10%. These results may provide guidance for reducing heat stress in industrial hot environment.

Calorimetry with heat flux transducers: comparison with a suit calorimeter

1983 ◽  
Vol 54 (5) ◽  
pp. 1361-1367 ◽  
Author(s):  
R. P. Layton ◽  
W. H. Mints ◽  
J. F. Annis ◽  
M. J. Rack ◽  
P. Webb
Keyword(s):  
Heat Flux ◽  
Heat Loss ◽  
Loss Rate ◽  
Human Subjects ◽  
Whole Body ◽  
Heat Loss Rate ◽  
Total Body ◽  
High Degree ◽  
Body Heat ◽  
Loss Rates

Regional and total body heat loss rates of human subjects at rest were measured simultaneously by means of an array of heat flux transducers and with a tube suit calorimeter. Conditions ranged from thermal comfort to strong cooling. A high degree of correlation was found between heat loss rates determined by the two independent techniques. For the head and arms, the transducer array system measured less heat loss than the suit. For the torso and legs, measurements by the two methods were equivalent. For the whole body, the transducer system yielded a heat loss rate 87% of the suit calorimeter value.

scholarly journals Modeling of Water Generation from Air Using Anhydrous Salts

Energies ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3822
Author(s):  
Shereen K. Sibie ◽  
Mohamed F. El-Amin ◽  
Shuyu Sun
Keyword(s):  
Mathematical Model ◽  
Relative Humidity ◽  
Water Absorption ◽  
Copper Chloride ◽  
Water Reservoir ◽  
Ambient Air ◽  
Water Harvesting ◽  
Atmospheric Water ◽  
Water Scarce ◽  
The Mathematical Model

The atmosphere contains 3400 trillion gallons of water vapor, which would be enough to cover the entire Earth with a one-inch layer of water. As air humidity is available everywhere, it acts as an abundant renewable water reservoir, known as atmospheric water. The efficiency of an atmospheric water harvesting system depends on the sorption capacities of water-based absorption materials. Using anhydrous salts is an efficient process in capturing and delivering water from ambient air, especially under a condition of low relative humidity, as low as 15%. Many water-scarce countries, like Saudi Arabia, receive high annual solar radiation and have relatively high humidity levels. This study is focused on the simulation and modeling of the water absorption capacities of three anhydrous salts under different relative humidity environments: copper chloride (CuCl2), copper sulfate (CuSO4), and magnesium sulfate (MgSO4), to produce atmospheric drinking water in water-scarce regions. By using a mathematical model to simulate water absorption, this study attempts to compare and model the results of the current computed model with the laboratory experimental results under static and dynamic relative humidities. This paper also proposes a prototype of a system to produce atmospheric water using these anhydrous salts. A sensitivity analysis was also undertaken on these three selected salts to determine how the uniformity of their stratified structures, thicknesses, and porosities as applied in the mathematical model influence the results.

COMPUTER MODELING OF THE STRUCTURE OF FOREST DRYING CHAMBERS, REDUCING HEAT LOSS

2020 ◽  
Vol 2020 (4) ◽  
pp. 60-67
Author(s):  
Boris Pruss ◽  
Viktor Romanov ◽  
Yaroslav Prozorov ◽  
Olga Pleskacheva
Keyword(s):  
Computer Modeling ◽  
Heat Loss ◽  
Heat Losses ◽  
Heat Energy ◽  
Insulating Materials ◽  
Sawn Timber ◽  
Drying Chamber

The paper presents the theory of calculating heat loss through the fences of timber drying chambers. The software for computer modeling of the process of transferring heat energy through the fences of the drying chamber, consisting of various heat-insulating materials, for calculating heat losses during drying of sawn timber is described. The efficiency of the use of modern heat-insulating materials to reduce heat losses during drying of sawn timber has been experimentally confirmed.

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