Analysis of Mingled Shell-side stream P M V

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 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 hnormal be the coefficient of heat transfer for simple flow past array of tubes. Asurf-total and DTM, 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.