Using CFD Technology to Simulate a Model of Human Thermoregulation in the Stable Temperature Environment

In the paper, the authors analyzed the solution of the differential equation of non-stationary heat conduction for an unbounded plate during the heat exchange of plate surfaces with the surrounding medium according to Newton’s law at a constant temperature of the medium. To use the results of solving the equations in the drying of thin flat materials, the dependence of the heat transfer coefficients on temperature and moisture content was studied. As a result of studying and analyzing a number of literature sources, the regularities of the change in the heat transfer coefficients during drying are established with high reliability. Studies of drying of thin wet plates of white and red clays with known heat transfer coefficients have shown that for small values of the heat transfer criterion of the Bio and small temperature gradients over the section of a thin material, application of the results of solutions of the heat transfer equations gives completely satisfactory agreement between the calculated and experimental values of the temperatures and the duration of drying. It is established that for small Bio numbers, the main factor is the external heat and mass transfer of the surface of the material with the surrounding medium and the rate of drying depends little on internal mass transfer. It is shown that the use of numerical methods for solving differential equations is possible with varying degrees of approximation only for accurate and reliable dependences of heat and mass transfer coefficients on moisture content and temperature. For a number of materials with known heat transfer coefficients, the use of analytical methods in calculations is of considerable interest and brings the theory closer to the practice of drying.

Heat and mass transfer in combined convective and far-infrared drying of fruit leather

The key local segments of human body for personalized heating and cooling

This study was aimed to improve the SO2 desorption effect of basic aluminum sulfate SO2-rich solution. Based on the desorption mechanism, we first used a falling film evaporation method to intensify heat transfer and mass transfer. Based on the falling film desorption heat and mass transfer model, we analyzed the falling film evaporation and desorption of basic aluminum sulfate SO2-rich solution inside the converging–diverging tube and the smooth tube and investigated the heat and mass transfer rules under different conditions. It was found as the quantity of SO2-rich solution increased, the heat transfer coefficient and mass transfer coefficient of falling film evaporation both increased, but the SO2 desorption efficiency decreased. With the rise of the heating temperature, the three indices all increased. With the rise of the inlet sulfur concentration, the three indices all increased. With the rise of the aluminum concentration, the three indices all gradually declined. With the rise of the alkalinity, the three indices all gradually declined. Comparative analysis showed the heat transfer coefficient and mass transfer coefficient of falling film evaporation and SO2 desorption efficiency were 17%–29%, 33%–69%, and 6.7%–16.3% larger inside the converging–diverging tube than the smooth tube, respectively, indicating the basic aluminum sulfate SO2-rich solution significantly outperforms inside the converging–diverging tube in terms of heat transfer and mass transfer. At the heating temperature of 108 °C, liquid film flow rate of 0.005 kg/s, sulfur concentration of 0.06 mol/L, aluminum concentration of 20 g/L, and basicity of 20%, the SO2 desorption efficiency inside the converging–diverging tube could reach a high level 94.2%, compared with only 83.7% inside the smooth tube. Moreover, correlations were obtained to predict the heat and mass transfer coefficients.

Numerical evaluation of the convective and radiative heat transfer coefficients for preterm neonate body segments inside an incubator

To protect the human body from extreme climatic conditions such as cold and hot environments, thermal jackets are used. In this study, thermal jacket with various material such as nylon, cotton , combination of nylon and cotton and polypropylene are considered for the simulation analysis to predict the temperature distribution from the skin surface to the jacket layer. The problem domain is composed of arms and chest which are modelled using Finite Element Method (FEM) and meshed into nodes and elements. Further , meshed geometry is analysed using Ansys software to predict the temperature distribution along the skin and jacket layer. It is found that combination of cotton and nylon yields better performance compared to other materials for both hot and cold environments.

Survival Under Heat Stress of Lines Selected for Fast and Slow Growth at Two Temperatures

Computation of airflow effects on heat and mass transfer in a microwave oven

The influence of liquid-side mass transfer on heat transfer and selectivity during surface and nucleate boiling of liquid mixtures in a falling film

Low air-side heat transfer coefficient (HTC) limits the performance of many heat exchangers. A new method is developed to obtain local air-side HTC of real heat exchangers without the use of complex experimental tools. The method relies on measuring mass transfer and applying the analogy between heat and mass transfer to determine heat transfer. A thin film coating is applied to the heat transfer surface which is exposed to a suitable trace gas, in this case, a 50 ppm ammonia-air mixture. The coating absorbs the ammonia and changes color. A detailed description of the new measurement technique is given, including the application of the fundamental heat and mass transfer correlations, evaluation of suitable coating formulations, determination of surface morphologies, and discussion of the optical principle to quantify color change. For laminar flow across flat plates, the new method results in experimental HTC that are within 17% of the Blasius solution.

Heat and mass transfer characteristics in a gas–slurry–solid fluidized bed

The primary goal of the current work is to model heat and mass transfer during mango drying in a wavy airflow dryer. By modifying the dryer walls, we were able to produce the undulating airflow (with V-shaped obstacles). With convective boundary conditions applied to all product surfaces, the explicit finite difference approach was used to study heat and mass exchanges in two dimensions during the drying of mango slices. During drying, the transfer coefficients are thought to fluctuate. Using EasyCFD software, the external flow, temperature, velocity, and pressure fields were then analyzed. This provided the profile of the heat transfer coefficient. These profiles were then utilized to calculate the mass transfer coefficient using the Shilton-Colburn analogy. Moreover, the code created to determine the heat and mass transfer coefficients in the product was used to derive the evolution of temperature and moisture content over time. The results allowed for the discovery of a new air flow in dryers called an undular flow and demonstrated how modifying the drying air stream enhanced heat transfer efficiency. By changing the air flow in the dryer, it was possible to achieve heat transfer coefficients ranging from 47.55 W/m²K to 357.38 W/m²K and mass transfer coefficients of 3.21 x 10-5 to 3.21 x 10-4 m²/s. When the outcomes of this investigation were compared to experimental results from the literature (under identical drying circumstances), a reasonable level of adequacy was discovered.

Two experiments were conducted to assess the ability for recombinant porcine somatotropin (rpST)-treated pigs to perform and cope with the demands of hot and cold environments. In the first experiment, finishing pigs were exposed to either a thermoneutral (TN; 18 to 21 degrees C) or a hot environment (H; 27 to 35 degrees C) for 35 d. In the second experiment, pigs were exposed to a TN or cold environment (C; 5 to 15 degrees C). The rpST delivered by a 6-wk prolonged-release system had no effect on ADG, whereas both H and C reduced ADG by 29.4 and 11.8%, respectively. In the first experiment, rpST-treated pigs consumed 17.6% less feed than control pigs, whereas rpST-treated pigs in H consumed 24.4% less feed than rpST-treated pigs in TN. Overall feed/gain ratios through the first 4 wk of both studies were improved by 21.8 and 14%, respectively, by rpST (P < .05) and were 24.3% poorer in C (P < .05) than in H. The changes in blood concentrations of pST, IGF-I, and IGF-II associated with rpST were not influenced by the different environments. Total body composition of rpST-treated pigs had increased amounts of protein (P < .05) and decreased amounts of fat (P < .05); H further reduced fat (P < .05). The C resulted in reduced protein content (P < .05). No evidence of thermal imbalance due to rpST was found as assessed by rectal temperature, respiration rate, and heat production estimated by indirect calorimetry and chemical analysis.

Thermodynamic performance and flow structures analysis of supercritical CO2 applied in a regenerative cooling channel mounted with mini-ribs

A numerical study has been conducted to explore the effect of a pressure-side winglet on the flow and heat transfer over a blade tip. Calculations are performed for both a flat tip and a squealer tip. The winglet is in the form of a flat extension, and is shaped in the axial chord direction to have the maximum thickness at the chord location, where the pressure difference is the largest between the pressure and suction sides. For the flat tip, the pressure-side winglet exhibits a significant reduction in the leakage flow strength. The low heat transfer coefficient “sweet-spot” region is larger with the pressure-side winglet, and lower heat transfer coefficients are also observed along the pressure side of the blade. For the flat tip, the winglet reduces the heat transfer coefficient locally by as much as 30%, while the average heat transfer coefficient is reduced by about 7%. In the presence of a squealer, the role of the winglet decreases significantly, and a 5% reduction in the pressure loss coefficient is achieved with the winglet with virtually no reduction in the average heat transfer coefficient. On the other hand, the suction-side squealer with constant width winglet shows lower heat transfer (reduction of 5.5%) and pressure loss coefficient (reduction of 26%) than its baseline counterpart.