Regulation of the temperature of an individual heat point by changing the speed of the asynchronous motor

THE PURPOSE. To develop and investigate a mathematical model of an operating object – an individual heat point with two methods of controlling the temperature of the coolant. In the first case, the control of the temperature of the coolant is considered, with the help of a control valve installed on a real object. In the second case, a more reliable and less energy-consuming solution is proposed – replacing the control valve with a frequency- controlled electric drive operating according to the proposed optimal algorithm. METHODS. When solving this problem, the method of computer simulation modeling, implemented by means of Matlab Simulink, was used.RESULTS. The article deals with the problems that arise during the operation of an individual heating point. Possible solutions to the problem associated with the failure of the control valve are given. A solution for regulating the temperature of the coolant is proposed, based on the use of a frequency-controlled electric drive of the electric pump. To implement the proposed solution, no redevelopment of the premises is required, only the installation of a frequency converter on the pump already available in the device of an individual heat station is necessary. CONCLUSION. The conducted research has a practical focus, since the proposed solution is implemented at the existing facility. The use of a frequency-controlled electric drive of a centrifugal pump made it possible to increase the reliability of the existing facility. The results obtained during the simulation allow us to draw a conclusion about the feasibility of using the proposed solution.

Research on the Forecast of Urban Underground Space Demand

Forecasting the capacity demand of underground space is the difficulty and a heat point in urban planning and urban underground space development. Through the survey data of Shanghai underground space capacity in 2006 and 2008, this paper conducts an empirical study on forecasting the capacity demand of underground space using thespatial regression model as the classical model by applying tools of STATA, SPSS and ArcGIS. The study indicates that the scale of underground space development and use is in a significant positive relationship with the population density and GDP per capita, but is not relevant with the price of real estate. The characteristics are apparently different in the underground space development and use in Shanghai between the central and the rural area. The underground space development in Shanghai is at the stage of rapid promotion, and will keep increasing at a high speed. The paper reveals the development law of Shanghai underground space development and the method of forecasting the capacity of underground space so as to provide theoretical analysis tool for development of underground space in Shanghai and other cities.

The Definition of Point Sources: Point Charge, Mass Point and Heat Point Source—A Generalized Sternberg Definition of Concentrated Forces

By considering the concept of point sources, such as point charge, mass point, and heat point source, we give a unified definition of these point sources with three conditions to judge what kind of distributed source in a small region can be taken as a point source by applying Sternberg's concept on concentrated forces. Comparing it with the traditional qualitative understanding of this concept, the definition gives a new condition with a very simple form. Counter-examples demonstrate that the traditional understanding of the point source is not sufficient and the new requirement should not be omitted.

INVARIANT SOLUTIONS AND THE CONSERVATION LAWS FOR THE HOT—POINT DEVELOPMENT MODEL

Analytical heat point development model is investigated. With the aid of group analysis, invariant solutions are obtained for many practically important cases. Conserved currents connected with associated linear equations are constructed.