Experimental Study of the Double Pipe Heat Exchanger for Heat Transfer and Pressure Drop Characteristics of the Grooved Tube

Abstract

Experiments are conducted to investigate the heat transfer and pressure drop characteristics of corrugated tubes and rod baffles in a shell-and-tube heat exchanger. One of the effective techniques to improve heat transfer is to use corrugated tubes. This article investigates rod baffles with varied corrugation depths and corrugated tubes for (1 start). In the heat exchanger's shell side, where a constant wall temperature was attained on the tube side, water was employed as the working fluid after being heated at the wall. Corrugation ratios (e/dh) of 0.1 and 0.13, pitch (p) of 10, 20, and 30mm, and two types (x/d) of 1.25 and 1.375 were used. The study was conducted throughout the Reynolds number turbulent range (4,000 to 24,000). The results manifested that the average Nusselt number of the corrugated tubes (pitch-10mm) for (x/d=1.25) increased by 25 and 55 percent for the corrugation depths of 0.1 and 0.13, respectively. The average Nusselt number for (x/d=1.375) is increased by 38% and 59% for the corrugation depths of 0.1 and 0.13, respectively. Nevertheless, the average friction factor of the corrugated tube with (e/dh) = 0.1 and 0.13 is higher than that of the smooth tube by 66% and 130%, respectively, and it decreases as the corrugation pitch and (x/d) are increased. When a corrugated tube and a rod baffle with a corrugated depth (e=2.1mm) and pitch (p=10mm) were used, the thermal enhancement factor was 1.9 for (x/d=1.25) and 1.97 for (x/d=1.375) at the same pumping power.

Keywords

• corrugated tube
• heat transfer enhancement rod baffle
• friction factor
• nusselt number heat exchanger
• pressure drop