TECHNICAL AND ECONOMIC EFFICIENCY OF COMBINED DISTRICT HEATING WITH LOCAL HEAT SOURCE FOR DISTRICT HOT WATER

The scheme of combined district heating systems is used, in which centralized heating is used for heating and local heat source is used for hot water supply. A mathematical model has been developed that allows to perform a comparative analysis of the technical and economic characteristics of two scenarios of modernization of the heat supply system: replacement of boilers, heat networks and pumps while using the traditional hot water supply scheme, and replacement of these elements in combination with the installation of a local hot water supply source that provides the hot water supply. hot water by means of a local heat network whose length is substantially smaller than the existing one. Electric heaters and solar collectors with electric heating are proposed as local heat sources. The advantages of combined district heating schemes on the planning horizon of 10 years are shown. The analysis of the influence of various factors on the advantage of the combined scheme of district heating is performed. The developed model can be used for preparation of feasibility studies of projects of energy efficient modernization of district heating systems. Ref. 4, Fig. 7, Tab. 1.

Local Heat Source Needed to Form Liquid Water Lake on Mars

Thermal modeling suggests that active magmatism in the past few hundred thousand years could account for the presence of a large lake previously hypothesized beneath the Red Planet’s southern ice cap.

Unsteady natural convection with entropy generation in partially open triangular cavities with a local heat source

Purpose The main aim of this work is to perform a numerical analysis on natural convection with entropy generation in a partially open triangular cavity with a local heat source. Design/methodology/approach The unsteady governing dimensionless partial differential equations with corresponding initially and boundary conditions were numerically solved by the finite difference method of the second-order accuracy. The effects of dimensionless time is studied, and other governing parameters are Rayleigh number (Ra = 103 − 105), Prandtl number (Pr = 6.82), heater length (w/L = 0.2, 0.4 and 0.6) and distance of heater ratio (δ/L = 0.3). Findings An increase in the Rayleigh number leads to an increment of the fluid flow and heat transfer rates. Average Bejan number decreases with Ra as opposed to the average Nusselt number and average entropy generation. High values of Ra characterize a formation of long-duration oscillating behavior for the average Nusselt number and entropy generation. Originality/value The originality of this work is to analyze the entropy generation in natural convection in a one side open and partial heater-located cavity. This is a good application for electronical systems or building design.