Enhancement of heat transfer using twisted tape insert in a plain tube

Abstract

The use of insert within a tube is one of the techniques enhancing the convective heat transfer coefficient at the expense of hydraulic loss penalty. This mutual effect which is a strong function of insert geometry and flow conditions is to be analyzed in detail to improve the overall system performance. This study presents a numerical investigation for analyzing the thermo-hydraulic characteristics of twisted tape insert in a plain tube (with a 13mm-diameter and 1200-mm-long) which is widely used in refrigeration applications where the compactness of the heating/cooling component is significant. The effect of twist ratio on the thermo-hydraulic performance was conducted for the Reynolds number range of 5,025−14,871 where most of refrigeration applications are operated in. The verification of the simulation results was compared to Dittus-Boelter empirical equation (for the plain tube case) and good agreement was obtained. Results indicate that the variation of the twist ratio between 6−9 increases the friction factor and Nusselt number 197−245%, 180−220%, 163−189% and 156−179%, and 32−54%, 28−46%, 28−33% and 28−33% relative to the plain tube case, respectively for the specified operating conditions. The performance evaluation criteria, which are measure of enhancing heat transfer against hydrodynamic forces, changed between 0.90−1.02, 0.89−1.00, 0.91−0.96 and 0.92−0.96 based on the twist ratio rise. The maximum enhancement in the performance evaluation criteria was obtained at the lowest Reynolds number and twist ratio. The performance evaluation criteria lower with increasing Reynolds number but can be increased by increasing the twist ratio.

An analysis of the impact of nanofluids on the cooling effectiveness of pin and perforated heat sinks

“…HS performance is highly influenced by factors such as fin dimensions, forms, quantity, arrangement, heat surface placement, and coolant type. Göksu et al [7,8] have obtained important results of heat transfer improvement by using passive methods, i.e., geometrical modifications, in their studies. Kuru [9] investigates the performance of triangular ribbed plate fin HS, focusing on their thermal efficiency, weight, volume, and cost reduction.…”

Variation in the enhancement of heat transfer with different fluids using twisted tape inserts

“…Optimizing Heat Transfer (HT) will help in the reduction of energy waste in a broader area of applications. Because of the rising consciousness for power savings, many researchers have been involved in HT enhancement, because an enlargement in HT rate leads to expanded machine performance [3], [4], this is a requirement for all thermal application systems. HT improvement methodology is categorized into several classes: compound, active, and passive [5].…”