Performance and Consistency of Circulating Warm Water Blankets for Rodents

General anesthesia as used for rodent research can have adverse effects on physiologic mechanisms. Thermoregulation is often greatly inhibited, with resultant deleterious effects on cardiac and respiratory function. These potential effects can be mitigated by providing external heat support. The circulating warm water blanket and associated heat pump are often used in rodent procedures. The current study demonstrated that the heating pump and water blanket require quality control assessment to ensure adequate function. Our data showed that of the 6 pumps tested, 5 were able to achieve a temperature thatmet or exceeded the documented thermoneutral zone for mice. Pumps required 20 min of warming to reach their maximal attainable temperatures for the designated user setting. Although the pumps reached a temperature that was sufficient toprovide external thermal support, only 1 of the 6 pumps reached the temperature that was set by the user during the trial.Surface temperatures across the water blanket were recorded to analyze whether a difference in heat support was influencedby animal placement along the water blanket; however, the location points did not yield statistically different results. Two pumps were eliminated from the study due to failure to pass the preparation phase of the trial. The results of this studysupport the need for facilities to establish quality control measures to ensure that heat support systems are functioning at a level required to maintain normothermia during anesthetic procedures.

Sensitivity analysis of temperature in heated soft tissues with respect to time delays

Axisymmetric tissue region heated by an external heat flux is considered. The mathematical model is based on the dual-phase lag equation supplemented by appropriate boundary and initial conditions. This equation, in relation to the Pennes’ equation, has two additional parameters, namely the relaxation time and the thermalization time. The aim of this research is to estimate the temperature changes due to changes of these parameters. To achieve this, sensitivity analysis methods are used. The basic problem and additional ones related to the sensitivity functions are solved using the implicit scheme of the finite difference method. The performed computations show that the temperature changes caused by changes in the relaxation and thermalization times are larger for higher values of the external heat flux and shorter times of its action.

Heat and moisture transfer kinetics and temperature during drying of fabrics

The methods of approximation of the curve of the drying rate of fabrics according to the methods of A. V. Lykov and V. V. Krasnikov are described. The results of processing experimental data on convective tissue drying are presented. Equations are given for determining the drying time of fabrics, the density of heat flows and the temperature of fabrics during the drying process. The equations for determining the drying coefficient and the relative drying rate are given. An analytical method for determining the temperature for the period of falling drying rate is considered. The comparison of the temperature values according to the results of analytical solutions with the values obtained by the experimental formula is given. It is shown that the number of Bio during drying of fabrics is less than one, and the main limiting factor is the external heat and moisture exchange of the evaporation surface from the surface of the material with the environment. Verification of the reliability of the calculated values obtained with experimental ones is presented. The discrepancy between the values is within 5 % of the accuracy of the experiment and processing.

Reducing the Natural Convection Inside an Enclosure Using a Concentric Internal Open Square

This paper presents the results of a numerical simulation for the natural convection inside an enclosure that has an inner open square at its center. The inner square is open at the top and connected to the ceiling of the enclosure. The open inner square distorts the convection patterns, slows down the flow, and provides a compartment to confine the fluid at the core of the enclosure. Ultimately, this lowers the local Nusselt number, Nu, along the hot wall, and reduces the heat flux through the enclosure. The analysis shows the effects of changing the dimensions of the inner square on the heat flux through the enclosure for a range of Ryleigh numbers from 103 to 106. Short-sided inner squares work as flow deflectors while long-sided inner squares provide compartments to accommodate new flow circulation at the core of the enclosure. The inner square is most effective when the length of its sides equals the width of the stagnant core inside the empty enclosure at the same Ryleigh number, and the heat flux at this condition is the lowest. Inner squares made of thermally conducting materials can reduce the heat flux through the enclosure by 70%, while adiabatic inner squares can reduce the heat flux by 90%. Inner squares reduce the external heat load on buildings when fitted inside the holes of hollow bricks used in building facades. The external heat flux can be lowered by 30%-55% depending on the square material and outer side temperature.

Visualization of physical and mathematical models of thermodynamic processes of single-phase flows using MATLAB to diagnose the condition of external heat supply networks

Nowadays, Russia has the longest heating network system in Europe (about 125 000 km in total). Given the constant growth in the volume of construction space, the length will constantly increase. Consequently, there is a request to increase the level of reliability of heat supply networks. It is possible to satisfy the request only by increasing the volume and quality of comprehensive diagnostics of heat supply networks with simultaneous reduction of time costs. This is possible only if a new generation of measurement and computing complex (MCC) is developed for the diagnosis of heat supply networks. The team of authors examines the features of the information environment in heat supply networks, separately noting the possibility of switching the flow from single-phase to multi-phase and back. The paper proposes to consider a solution to a problem that arises when trying to visualize physical and mathematical models of thermodynamic processes of single-phase flows using MATLAB. It consists in the fact that the desired physical and mathematical model should describe the thermodynamic processes of a single-phase flow, but taking into account that this flow moves in the external heat supply network. The possibility of using the MATLAB functional environment for developing a model based on visually oriented programming is considered in detail, which allows us to lay the foundations for further forecasting the development of the heat supply system.

Finite Element Analysis (FEA) of Local Hyperthermia on Soft Tissue

Finite Element Analysis (FEA) is a method for simulating a local hyperthermia (HT) effect on the soft tissue liver by exposing it to an external heat higher than normal core body temperature. Local HT treatments are most commonly used to treat cancer tissue smaller than 3 cm in size by using radiofrequency ablation (RFA) technique. The radiofrequency probe provides an intense external heat source within the target zone with temperatures exceeding 50 °C, but its maximum temperature should not approach 100 °C. In this paper, the main idea is to study the effect of tumor diameter size on the exposure time, thermal exposure intensity and applied voltage. There are five (5) different tumor diameter tissue sizes that would be treated: 1 cm, 1.5 cm, and 2 cm of tumor tissue diameter treated with a monopolar of plain electrode, and 2 cm, 2.5 cm, and 3 cm of tumor diameter tissue treated with 4-prong retractable antennas of an electrode. The findings showed that the exposure time is influenced by the tumor diameter tissue and the voltage applied, with the bigger tumor diameter tissue necessitating the longest time exposure with a high voltage. The temperature range of 50-100 °C has been given by all of the voltage supplied. Both electrodes provide thermal damage between 6-20 minutes, which is 6 – 18.5 minutes for a plain electrode with a voltage supply of 20-35 V applied to 1cm, 1.5cm and 2 cm of tumor diameter tissue, and 10.5 – 12.5 minutes for a 4-prongs electrode with a voltage supply of 22-45 V applied to 2 cm, 2.5 cm and 3 cm of tumor tissue.

Effect of external heat source on temperature and moisture variation for composting of food waste

This paper investigates the outcome of having an external heat source on temperature and moisture variations in the food waste composting process. Food waste accumulation is a growing concern in many countries. Converting food waste into usable compost is a more desirable tactic than dumping to crowded landfill sites. Closed composting was applied in this work, which relies on a controlled but uninterrupted airflow during the organic material degradation process. However, undesirable odour released at low aeration rate due to low temperature and high moisture content found in the compost. Finding the ideal aeration rate with the least possible loss of moisture is needed, which was discussed in this paper. The vegetable-fruit waste used in the experiment was given an aeration rate of 0.3 L/min at a moisture setting of 60% and 70%. For 15 mins/day, the forced aeration was carried out at 3-day intervals. Results showed that 0.3 L/min with 60% and 70% moisture content attained best temperature peaks of 32.4°C and 31.6°C, respectively at day 13 for 28 days composting. A strong odour continued to exist with the compost and was mitigated by using an external additional heat source (light bulb). The light bulb also helped to provide a higher temperature for the compost of 41.5°C by day 1 for 10 days composting.

Investigation of Heat Transfer in a Large-Scale External Heat Exchanger with Horizontal Smooth Tube Bundle

In the research work, energy transport between a dense fluidized bed and submerged horizontal tube bundle is analyzed in the commercial external heat exchanger (EHE). In order to investigate the heat transfer behavior, the authors carried out eight performance tests in a fluidized bed heat exchange chamber with a cross-section of 2.7 × 2.3 m in depth and width and a height of 1.3 m. The authors have been developing a mechanistic model for the prediction of the average heat transfer coefficient, which includes the effect of the geometric structure of the tube bundle and the location of the heat transfer surface on the heat transfer rate. The computational results depict that the average heat transfer coefficient is essentially affected by superficial gas velocity and suspension density rather than bed particle size. The empirical correlations have been proposed for predicting heat transfer data since the existing literature data is not sufficient for industrial fluidized bed heat exchangers. On the basis of the evaluated operating conditions of an external heat exchanger, the optimal conditions where heat transfer occurs could be deduced. The developed mechanistic heat transfer model is validated by experimental data under the examined conditions.