Numerical Analysis on Natural Convection Heat Transfer in a Single Circular Fin-Tube Heat Exchanger (Part 2): Correlations for Limiting Cases

Abstract

This research focused on the correlations associated with the physics of natural convection in circular fin-tube models. The limiting conditions are defined by two conditions. The lower limit ( D o / D → 1, s/D = finite value) corresponds to a horizontal circular tube, while the upper limit ( D o / D → ∞, s/D << 1) corresponds to vertical flat plates. In this paper, we proposed a corrected correlation based on empirical result. The circular fin-tube heat exchanger was divided into the A and B types, the categorizing criteria being D o / D = 1.2 , where D and D o refer to the diameter of the circular tube and the diameter of the circular fin, respectively. Moreover, with the computational fluid dynamics technique used to investigate the limiting conditions, the parametric range was extended substantially in this research for type B, namely 1.2 < D o / D ≤ 10. The complex correlation was also simplified to the form Nu L = C Ra s n , where C and n are the functions of the diameter ratio D o / D .

Modeling of IGBT junction temperature based on load torque variation in induction motor

“…The switching frequency is 5 kHz, the fundamental frequency is 60 Hz, the DC-link voltage is 400 volts, the ambient temperature is 25 o C, and the IGBT's maximum temperature is 150 o C. The cooling system's fan speed is 1000 ft/min. In this study, four load torque values (10,15,20,25) Nm are used of this system to monitor changes in the junction temperature. It is found that the value of the junction temperature increases as the load torque rises; the maximum value of TJ was recorded at a torque of 10 Nm is (64.5 ℃), it recorded (71.7 ℃) at a torque of 15 Nm, it recorded (77.24 ℃) at a torque of 20 Nm and recorded (82.46 ℃) at a torque of 25 Nm.…”

“…As a result, the thermal resistance of the IGBT module's entire heat transfer process can be divided into only three components. The IGBT chip's thermal resistance to the heat sink is initially measured as its contact thermal resistance, followed by the heat sink's solid thermal resistance and the heat sink's convective heat transfer resistance to the ambient [9], [10].…”

A review on the modification of circular fin and tube heat exchangers through new innovative fin shapes

“…At Ra numbers 15, shorter fins or a greater s/D ratio improve functionality. In the second part of their study [78], they focused on the correlation of various circular fins. The circular fin-tube heat exchanger was categorised by Do/D = 1.2, where D and Do represent the tube and fin diameters, respectively.…”

Design and Analysis of the IGBT Heat Dissipation Structure Based on Computational Continuum Mechanics

“…Therefore, the thermal resistance of the entire heat transfer process of the IGBT module can be simplified to three parts. The first part is the contact thermal resistance of the IGBT chip to the heat sink, the second part is the solid thermal resistance in the heat sink, and the third part is the convective heat transfer resistance between the heat sink and the outside air [ 15 , 16 , 17 ].…”