Entransy Dissipation Analysis and New Irreversibility Dimension Ratio of Nanofluid Flow Through Adaptive Heating Elements

Fikret Alic

doi:10.3390/en13010114

Abstract

A hollow electric heating cylinder is inserted inside a thermo-insulating cylindrical body of larger diameter, together representing a single cylindrical heating element. Three cylindrical heating elements, with an independent electrical source, are arranged alternately one after the other to form a heating duct. The internal diameters of the hollow heating cylinders are different, and the cylinders are arranged from the largest to the smallest in the nanofluid’s flow direction. Through these hollow heating cylinders passes nanofluid, which is thereby heated. The material of the hollow heating cylinders is a PTC (positive temperature coefficient) heating source, which allows maintaining approximately constant temperatures of the cylinders’ surfaces. The analytical analysis used three temperatures of the hollow heating cylinders of 400 K, 500 K, and 600 K. The temperatures of the heating cylinders are varied for each of the three cylindrical heating elements. In the same arrangement, the inner diameters of the hollow cylinders are set to 15 mm, 11 mm, and 7 mm in the nanofluid’s flow direction. The basis of the analytical model is the entransy flow dissipation rate. Furthermore, a new dimension irreversibility ratio is introduced as the ratio between entransy flow dissipation and thermal-generated entropy. This paper provides a suitable basis for optimizing the geometric and process parameters of cylindrical heating elements. An optimization criterion can be maximizing the new dimensionless irreversibility ratio, which implies minimizing thermal entropy and maximizing entransy flow dissipation.

Highlights

In many electric heaters, whose function is based on the resistance generating heat, different fluids are used for heating
We analytically modeled the thermal interaction between the heating elements and the nanofluid’s flow
For the selected heating system of three heating elements, with different temperatures of the surfaces and different internal diameters, we performed the analytical modeling of the characteristic internal surfaces and different internal diameters, we performed the analytical modeling of the thermal quantities of this system

Summary

Introduction

In many electric heaters, whose function is based on the resistance generating heat, different fluids are used for heating. The shapes and dimensions of these heaters are different and depend on their application. The overall efficiency and reliability of electric fluid heaters depend on several factors. The most common factors are fluid velocity, the shape and dimensions of the heating surfaces, and the temperature difference between the heating surfaces and the fluids. In this regard, researchers have been investigating different ways to maximize the efficiency of convective fluid heating. Fluids are often used for heating in heaters whose principle is based on thermal radiation. The pipe fitted with different rings in order to enhance

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Conclusion