Abstract
Based on thermal value theory, the aim of this paper is to deduce the theoretical formulas for evaluating the energy effective utilization degree in technological pyrological processes exemplified by metallurgical heating furnaces. Heat transfer models for continuous heating furnaces, batch-type heating furnaces, and regenerative heating furnaces are established, respectively. By analyzing the movement path of injected infinitesimal heat attached on steel or gas, thermal value equations of continuous, batch-type, and regenerative heating furnaces are derived. Then the influences of such factors as hot charging, gas preheating and intake time of heat on energy effective utilization degree are discussed by thermal value equations. The results show that thermal value rises with hot charging and air preheating for continuous heating furnaces, with shorter intake time when heat is attached on steel or longer intake time when heat is attached on gas for batch-type heating furnaces and that with more heat supply at early heating stage or less at late stage for regenerative heating furnaces.
Highlights
When studying thermal science and engineering, two types of energy utilization processes with different characteristics should be clearly distinguished
The results show that thermal value rises with hot charging and air preheating for continuous heating furnaces, with shorter intake time when heat is attached on steel or longer intake time when heat is attached on gas for batch-type heating furnaces and that with more heat supply at early heating stage or less at late stage for regenerative heating furnaces
Where Stg is the Stanton number for gas, and Stg0 is the Stanton number for gas when heat exchange area is A0, Equations (5) and (6) can be rewritten as Equations (5)-(8) are thermal value equations for continuous heating furnace; and Equations (5) and (7) are suitable for injected heat attached on steel while Equations (6) and (8) are suitable for injected heat attached on gas
Summary
When studying thermal science and engineering, two types of energy utilization processes with different characteristics should be clearly distinguished. One is energy conversion processes; the other is technological pyrological processes [1]. Thermal efficiency has been used to evaluate the energy effective utilization degree of energy conversion processes [2,3]. Thermal efficiency for technological pyrological process is different from that of energy conversion process [1]; and a conflict between thermal efficiency and specific energy consumption appears in some cases [4,5]. In this paper, heating furnaces in metallurgical industry, as technological facilities, are selected to study the evaluation method for energy utilization processes. Ory combining energy conservation principle and heat transfer theory to evaluate the energy effective utilization degree in technological pyrological processes.
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