Experimental studies on effect of Orientation of tubes on performance of Shell and tube heat exchangers

Abstract

Shell and tube heat exchangers are widely used in process industries, nuclear reactors, refineries, air conditioning and much more. This research aims at evolving a heat exchanger which is capable of exchanging heat effectively with a little or no increase in pressure drop without increasing the heat transfer area. Literature reveals that heat transfer is usually enhanced at the cost of increased pressure drop owing to increased pumping power. This research focuses on a Hybrid Double Cross Flow (HDCF) heat exchanger which has been developed from a previously reported Double Cross Flow (DCF) heat exchanger. The HDCF configuration has two sets of serpentine tube bundles which by themselves are orthogonal to each other and to the shell side fluid flow. However, these tube bundles were inclined so that the inline arrangement is avoided and the dual orthogonal flow is maintained. This dual orthogonal flow in the shell side results in better mixing with lesser directional changes leading to higher heat transfer rate when compared with the conventional staggered configuration wherein the serpentine tube bundles are parallel to each other and are perpendicular to the shell side fluid only. Experiments were conducted on the staggered and HDCF configurations with air as the cold shell side fluid and water as the hot tube side fluid. The velocity of the shell side fluid was varied between 1.01 to 1.76 m/s. The inlet temperature of the hot fluid ranged from 89.4and#8451; to 95.2and#8451; while the inlet temperature of the cold fluid was found to range from 37.3and#8451; to 42.1and#8451;. newlineThe experimental study performed suggested that the HDCF heat exchanger fared better than the staggered arrangement. The heat transfer rate was found to be higher for both the parallel and counter flow configurations in the HDCF arrangement. The HDCF parallel yielded a maximum of 46% increase in heat transfer rate whereas the HDCF counter was found to yield a maximum of 55 % increase in heat transfer rate when compared with the staggered parallel configuration newline