Modeling helped to improve the configuration of an autonomous heat supply unit

December 28, 2017

Scientists from Ural Federal University and Karaganda State Technical University modeled the operation of an autonomous heat supply unit and suggested some improvements. For more details about the study please refer to Energy Procedia journal.

In their article the authors of the study presented a mathematical model describing the work of an electrical technological unit for autonomous heat supply (EKAT). The dimensions of the unit range from 0.811 m to 1.522.5 m. It can be used in standalone heating, water supply, and air conditioning systems. The unit is green and easy to operate and allows a user to set a preferred working regime.

"This is one of the possible promising options for decentralized heating based on unconventional energy sources," added Joseph Breido, a co-author of the work and professor of Karaganda State Technical University.

EKAT transforms electrical energy first into mechanical energy (the pressure of liquid under the influence of pumps), then into the energy of flowing liquid, and finally into heat energy. The authors of the article focused on the stage of transformation from mechanical energy into heat. In order to be able to calculate different parameters of such system's operation, one has to take lots of measurements, including temperature, pressure, and liquid flow speed. A mathematical model makes this work faster and cheaper. The accuracy of the model was verified in the course of experimental studies.

Structural units of EKAT secure the flow of the working liquid (water) in a closed heat-producing loop system. At the same time the effect of cavitation (formation and collapse of gas bubbles) is observed in the Cavitator construction element in the tube reactor. As a result, the temperature of the working liquid in the loop slightly increases. The construction of the Cavitator is a patented know-how.

Using the model, the team was able to determine all characteristics required for maximum heating and efficient energy transformation. The total coefficient of performance in EKAT is around 0.8-0.9, i.e. from 80% to 90% of consumed energy is transformed into heat.

Based on experimental measurements, the scientists developed 3D models of working fluid flow inside the unit. Such models help find marginal conditions for solving physical and mathematical problems. Standard physical models of gas and liquid flows and complex calculations covering temperature changes and energy transfer were used to visualize liquid flows. The models allowed the scientists to set different parameters: temperature, pressure, flow speed, liquid properties, and initial temperature of the unit. Comparing calculation results with the data obtained in experiments, the team confirmed the accuracy of the software and its fitness for studying liquid flows and designing equipment.

"In the course of experimental studies we've also set and solved a task of assessing the influence of rotation speed of a variable frequency drive in a pumping unit both on the operational properties of EKAT and on power consumption during the generation of heat energy in amounts sufficient for comfortable autonomous heat and hot water supply to residential and office premises," said Anatoly Zyuzev, a co-author of the work and professor of the electric drive department of Ural Federal University.

Based on the obtained results, the scientists were able to suggest improvements to the configuration of EKAT to make it more efficient. First of all, they are associated with the Cavitator and the vortex tube. For example, changing the size of blades of the Turbine located in front of the Cavitator from six to eight centimeters leads to considerable increase in cavitation intensity and therefore to the growth of temperature.

Ural Federal University

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