INVESTIGATION OF IN TWO TUBE CROSS BOILING HEAT TRANSFER COEFFICIENT BUNDLES UNDER POOL AND LOW FLOW VELOCITY CONDITIONS

Abstract

The chracteristics of boiling outside tube bundles are important in a large variety of industrial heat exchange equipment. These include various types of reboilers and flooded evaporaters used in power plants and many chemical, refrigeration and air conditioning systems.-'hough lot of research work is available in leterature concerning boiling heat transfer over a single tube but the results obtained from it can not be directly applied to design multitube boiling heat exchange equipment effciently. This is due to the fact that boiling in a tube bundle is quite different from that on a single tube on account of changed thermal and flow field environment. Vapour bubbles rising up from the lower tubes in a bundle agitate the flow around the upper tube vigrously and make the boiling phenomena very complex.- _ Very limited work is available in the liteature concerning local boiling heat transfer from a tube in the bundle and a Lot more is needed to study this under a wide range of system and operating conditions to understand the phenomena more clearly and for designing the boiling heat exchange equipment more eff~ciemtLyl- • . . In view of this the present experimental investigation was under taken to collect the boiling data over two horizontal plain tubes heated independently and placed one above the other in a• large channel. The effect of heat flux, cross flow velocity and pitch distance on boiling heat transfer coefficient of each tube was analysed. The experiments were performed for the following operating conditions.