1. Thermo-economic Optimization of STHE P M V Subbarao Professor Mechanical Engineering Department I I T Delhi Minimizing capital and operating costs of shell and tube Heat Exchangers…..

2. Shell and Tube as a Thermal System Two major cost components of a heat exchange system are : 1. Capital, operating and maintenance costs of the pump/compressors. 2. Capital and maintenance costs of the heat exchanger.

3. Case Study :Total Cost Minimization 1382.51245 21833 13531199 2143564540 66411

4. Thermodynamic Strategy for Lowering Cost Selection of Shell Side Gas Pressure

5. Cost Analysis of Heat Exchanger Operation The cost of owning and operating a heat exchanger is the sum of: The cost of providing the heat transfer surface, C HT : This cost is taken as proportional to heat transfer area. The costs of maintaining the flow through it, C pump : This one is assumed as proportional to the pumping power. The cost of heating or cooling effect supplied to the exchanger C maint : This one is represented by an amount in proportion to the heat duty of the exchanger. An optimum design would be defined as an exchanger which has the maximum ratio of the heat duty to the cost

6. Total Cost of SHTE The optimum design is defined as an exchanger which has the maximum ratio of the heat duty to total cost.

7. Define C Normalizing C using a reference cost function:

8. Objective function

9. Independent Variables for Objective Function The area and pumping power vary considerably with respect to baffle space. As the baffle spacing is reduced, the pressure drop increases at a much faster rate than does the heat transfer coefficient. Thus, due to the considerable pressure drop, the pumping power cost increases as the area cost decreases. This means that there will be an optimum value of baffle spacing corresponding to minimum dimensionless F.

10. Heat Transfer Area Vs Baffle Spacing B/D s

11. Required Pumping Power Vs Baffle Spacing B/D s P/P max

12. Heat Transfer Area Vs Baffle Spacing B/D s P/P max

13. Normalized required heat transfer area vs dimensionless baffle spacing for four different pairs of sealing strips. B/D s

14. Normalized pumps power consumption vs dimensionless baffle spacing for four different pairs of sealing strips. P/P max

15. Scope for Parametric Study A parametric study for obtaining the optimum design should be made for all types of single phase shell and tube heat exchangers (fixed tube sheet, floating head and U tube) in a wide range of normal operational conditions. Tube and shell diameter, tube pitch, number of tube passes, tube arrangement, baffle spacing and number of sealing strips should be varied for all recommended values. The heat duty and viscosity coefficient of both streams should also be varied extensively. A collection of optimal designs is a treasure of data base for a designer.

16. How to convert Data Base into Knowledge Base Is it possible to identify the technical characteristic of the optimized design. A correlation of non-dimensional variables.

17. Physics of Optimal Solution : E type SHTE W1W1

18. Thermo-economics of Optimal Designs E type SHTE Floating Head SHTE U tube SHTE

19. Generality of Optimal Design W1W1

20. Experience Vs Optimization : E Shell Baffle spacing in optimal designs Baffle spacing in experience based Design

21. Experience Vs Optimization Baffle spacing in optimal designs Baffle spacing in experience based Design