Operation of Looped District Heating Networks

The study presents a methodology for the optimal operation of district heating networks with a circular conduit system. The authors discuss this this topic in an absolutely general form. By a special statement and solution of Kirchhoff Laws, node equations and loop equations, the hydraulic end point of the circle is determined, including the supply ratio of the consumer located at the hydraulic end point. Two objective functions are stated by the authors; one of them for the minimum of flow work, and the other for the minimum of power supplied. It is demonstrated that the objective functions yield different results. Theoretically more economical operation is ensured by the flow pattern resulting from the minimization of the power supplied

The newest results of heat conduction theory

This paper gives a detailed system theoretical treatment of the heat flux theory in the linear heat conduction based on the Laplace transformation method. By restricting the investigations to the simplest geometrical structures occurring in the practice, the authors prove the criteria guaranteeing the existence of the convolutional representations of the heat flux depending on the known temperature

The amount of extractable heat with single U-tube in the function of time

Heat pumps can be used for different purposes in building services. They obtain heat from the environment of lower temperature (e.g. air, water, earth) and transfer it into the building at a higher temperature. The heat of the ground can be the primary energy source of the heat pumps. We extract this heat with the help of ground heat exchangers. These exchangers are the U-tubes, which are either single or double. In our paper we deal with the problem of the extractable heat from the ground with these heat exchangers. We show a simple calculation method for the temperature change in the heat carrier fluid and for the overall thermal resistance of the U-tube

Description of the gas and service water consumption process by means of probability calculation

The characteristics of random gas and service water consumption of individual consumer groups (quantity, intensity, simultaneity, etc.) are probability variables in the mathematical sense. In scheduling gas and service water consumption, the chances of the realisation of the characteristics and the probability distribution also have to be determined. The authors relate the determination of scheduled values to the extent of assumption of risk. In the study they present new methods based on the theory of stochastic processes for describing the gas consumption of individual consumer groups and for determining the probability distribution of consumption values. They also show correlations to describe gas and service water consumption as the basis of the total heat load of gas appliances and cold or hot water fixtures

Extending the Validity of Basic Equations for One-dimensional Flow in Tubes with Distributed Mass Sources and Varying Cross Sections

Flow problems are solved using so-called fundamental equations and the corresponding initial and boundary conditions. The fundamental equations are the motion equation, the continuity equation, the energy conservation equation, and the state equations. In our paper, we extend the validity of the equation of motion used to describe one-dimensional, steady-state tubular flow to a case in which the mass flow of the medium changes along the tubular axis during the flow. Such flows occur in perforated and/or porous pipes and air ducts. The research in this direction was motivated by the fact that the extension and formulation of the equation of motion in this direction has not been carried out with completely general validity. In the equation of motion used to solve the problems, the isochoric and isotherm nature were assumed. In our paper, we present fundamental equations that formulate differential equations to describe polytrophic and expanding flows

Basic Flow Differential Equations applied in Building Service Engineering

In this article basic flow equations will be presented to describe the flow behaviour of various mediums, like gas, ideal gas, wet steam, ... etc. The equations constitute a system of simultaneous differential equations. The solution of this sytem is here not discussed. The Appendix gives a clearly arranged synopsis of the differential equations of flows under different conditions

The Advantages of Fuzzy Control for Heat Pumps Systems

Application of fuzzy control has been observed in various engineering fields due to its ability to handle uncertainties and non-linearities. In this study, the advantages of using fuzzy control in heat pump systems are being investigated. Specifically, the performance of a heat pump system with a conventional proportional-integral-derivative (PID) controller is being compared to that of a heat pump system with a fuzzy logic controller. It has been demonstrated by the results that the fuzzy control-based heat pump system offers better performance in terms of energy efficiency, temperature control, and overall system stability. This study contributes to the understanding of the potential benefits of fuzzy control-based heat pump systems and provides a foundation for further research in this area

Determination of optimal pipe diameters for radial fixed-track district heating networks

This paper presents the basics of Bellmann’s dynamic programming, to be applied for radial fixed-track district heating networks. A decision-making model thereof is produced, and Garbai’s scaling method [1] is applied in a new, narrower interval by using a tagging method well-known from computer science. Thereby the result yielded coincides with that of the previous method, but the number of calculations to be performed is reduced considerably