Design Analysis and Comparative Performance of Variable Pitch Tube in Tube Conical Spiral Heat Exchanger

Abstract

Lower heat transfer rate in heat exchangers as a result of fouling is a common problem in process industry. Shell and tube heat exchanger are subjected to fouling as result of prolonged use as the materials get deposited on the heat transfer surfaces or wetted area of the tubes and also occupies more space. Fouling brings down the heat transfer rate and effectiveness of the heat exchanger. Requirement of heat exchangers used in process industry, chemical industry applications is that there should be no contamination and lesser fouling. The above problem is addressed in our project. The spiral conical tube in tube heat exchanger offers the best compactness although the pumping power required is slightly on the higher side. The spiral conical tube in tube heat exchanger design is a challenge to manufacture so also difficult to clean over time for maintenance. The problem of fouling is easily dealt with in the project, by addition of variable pitch where in the shape geometry of the spiral will be changed from a flat spiral to a conical frustum. The geometry of the tubes plays a significant part in design and development of the heat exchanger. Paper work discusses the design & analysis of inner and outer tube of the heat exchanger where in the copper tube is wound in a spiral shape and hot fluid is always passed from inside of spiral to outside of spiral, but path of the cold fluid be changed to attain the parallel flow or counter flow configuration. The modeling is done using Unigraphix Nx-8 and analysis has been done using Ansys work bench 16.0. Test and performance comparison has been done in counter flow configuration for three pitch positions namely 0 mm (close coil), 10mm and 20 mm respectively.