Analysis of Mingled Shell-side stream P M V Subbarao Professor Mechanical Engineering Department I I T Delhi Splitting of A Circuitous Flow into Simple Flow Structures……

Shell-side stream analysis On the shell side, there is not just one stream. There are essentially two models that address the flow on the shell side. The ideal flow and real flow models. Ideal Shell side flow A nearly ideal flow can only exist in a heat exchanger if it is manufactured with the special mechanical features.

Shell side Real Flow When the tube bundle employs baffles, the velocity of fluid fluctuates because of the constricted area between adjacent tubes across the bundle. Only part of the fluid takes the desired path through the tube bundle, whereas a potentially substantial portion flows through the ‘leakage’ areas. However, these clearances are inherent to the manufacturing and assembly process of shell-and-tube exchangers, and the flow distribution within the exchanger must be taken into account.

Multi-Stream Shell Side Flow The shellside calculations are far more complex than those for the tubeside. This is mainly because on the shellside there is not just one flow stream but one principal cross-flow stream and four leakage or bypass streams. There are various shellside flow arrangements, as well as various tube layout patterns and baffling designs, which together determine the shellside stream analysis.

Main Flow Stream Stream B 1 is the main effective cross flow stream, which can be related to flow across ideal tube banks. As the main stream travels inside, the quantity of the main stream increases and becomes Stream B. There are tributary streams to stream B 1. These tributary streams are called Stream B.

Main Stream Tributaries : Stream C Stream C is the tube bundle bypass stream in the gap between the tube bundle and shell wall. Flow areas for stream C.

Leakage Flow Streams There are three different shell side leakage flow streams in a baffled heat exchanger Stream A is the leakage stream in the orifice formed by the clearance between the baffle tube hole and the tube wall. Stream E is the leakage stream between the baffle edge and shell wall. Stream F is the bypass stream in flow channel partitions due to omissions of tubes in tube pass partitions.

Leakage Streams A Flow areas for stream A.

Leakage Streams E and F Stream F happens in a multiple pass (1-2, 1-4) heat exchanger

Network of Sub-flows with Same Pressure Drop

Arithmetic Confluence Model Conservation mass: For A single Phase flow: Convective Heat Transfer Rate:

Analysis of Stream-wise contribution to Heat Exchange. Let h normal be the coefficient of heat transfer for simple flow past array of tubes. A surf-total and  T M,shell-total will be overall conditions.

Equivalent Stream Participation Potential Model If the total shell side mass flow travels as main stream, then the Hx will have Maximum (basic normal) capacity. Due to the division of the flow into number for tributaries, the overall capacity is different from basic normal or less than the Maximum possible capacity. Define equivalent (modified) mass flow, which is a fraction of actual mass flow having same flow geometry. Similarly modified (overall) capacity:

Multiplicative Participation Model: A Multiplicative Relation is always an Exact Function, also called as Pffafian Function. A Best way to represent Characteristics of A Thermodynamic System.