Temperature and Velocity Changes Across Tube Banks in One-directional and Bi-directional Flow Conditions

Abstract

The back-and-forth movement of flow in oscillatory flow condition that can be found in blood flow, thermoacoustic energy system and ocean wave can be categorized as bi-directional flow condition and heat transfer in this flow condition is not well understood. This paper reports an experimental investigation that compares temperature and velocity values between the onedirectional (the usual flow condition) and the bi-directional flow conditions. The experiment was done using thermoacoustic's standing wave rig with two different drivers to drive the one-directional flow and bi-directional flow conditions in the test rig. Results, that were recorded using piezoresistive pressure sensor, type-K thermocouple and hotwire anemometer, indicate that care should be exercised when calculating heat transfer in bi-directional flow conditions as the temperature and velocity changes are different compared to the one-directional flow condition. Differences were recorded to be within the range of 77% for temperature and 59.5% for velocity, presumably due to the different behavior of forced and natural convection effect as flow conditions changed.

Experimental Study on The Performance of One-Directional and Bi-Directional Flow Conditions Across In-Line Tube Banks Heat Exchanger

“…The purpose of the current investigation is to evaluate the effect of changing flow conditions on heat transfer performance across tube banks through experimental investigations. Earlier investigations confirmed that the bi-directional flow exhibits different velocity and temperature behaviors across the staggered tube banks heat exchanger compared to that of the one-directional flow condition [10,26,27]. The numerical results as shown in ref [27] provided insights into fluid dynamics aspect that supplement the experimental findings of [10].…”

“…Since the flow in this promising thermoacoustic energy technology is bi-directional in nature, it is therefore important to understand the heat transfer nature between the heat exchanger and the flow when it is placed in thermoacoustic environment. The heat transfer performances of tube banks with staggered arrangement under one-directional and bi-directional flow conditions were reported earlier [10]. The change of orientation of the tube banks changes the fluid dynamics of flow around the tube banks and therefore the heat transfer behavior is expected to be different too.…”

“…Earlier investigations confirmed that the bi-directional flow exhibits different velocity and temperature behaviors across the staggered tube banks heat exchanger compared to that of the one-directional flow condition [10,26,27]. The numerical results as shown in ref [27] provided insights into fluid dynamics aspect that supplement the experimental findings of [10]. Mikheev et al, carried out an experiment on the heat transfer performance of oscillating flow around a cylinder, and the findings showed that oscillation of an incoming flow might increase heat transfer [28].…”

“…Flows around tube bundles with a large number of tubes, on the other hand, have been the subject of a great deal of experimental and numerical efforts. The in-line [7,8], staggered [9][10][11], rotating square [12], regular triangle [13,14], and parallel triangle [15] are a few of the array designs that were investigated by researchers. The worldwide waste heat recovery market is being boosted by thermal industries such as petrochemical plants.…”

Design of Cooling System on Brushless DC Motor to Improve Heat Transfers Efficiency

“…Increasing motor efficiency is the most influential thing and must be considered in BLDC electric motors. Efficiency is always related to heat transfer and performance on BLDC motors 28) , so that the better the heat transfer efficiency, the better the cooling system [29][30][31] . One of the benchmarks of efficiency in a BLDC motor is heat transfer to the motor caused by the load received by the motor and the use of maximum speed, so it is one of the crucial factors in an electric motor design 32) .…”