2ME377 Heat Exchanger

A True Mediator !!!A Device which Enhanced the Utility of Fire!!!

BYA M Lakdawala

Asst ProfMechanical Engineering Department

Nirma University

Fire Can only Heat Solids !!!!!

EARLIEST TYPES OF HX : COOKING

• Primitive humans may first have savored roast meat by chance, when the flesh of a beast killed in a forest fire was found to be more palatable and easier to chew and digest than the customary raw meat.

• They probably did not deliberately cook food, though, until long after they had learned to use fire for light and warmth.

• It has been speculated that Peking man roasted meats, but no clear evidence supports the theory.

• During Palaeolithic Period, Aurignacian people of southern France apparently began to steam their food over hot embers by wrapping it in wet leaves.

• Crude procedures – as toasting wild grains on flat rocks and using shells, skulls, – or hollowed stones to heat liquids.

• Introduction of pottery during the Neolithic Period.• A paste, toasted to crustiness when dropped on a hot stone, made the

first bread.

Scientific Evolution of HEAT EXCHANGERS

Towards a True Adiabatic Communication !!!

The First Heat Exchanger

The Plain Cylinder Boiler:

•The first real advancement in heat exchanger came about with the invention of the Plain Cylinder Boiler. •It was a simple design and easily constructed.•As its name implies, the Plain Cylinder Boiler is a long metal cylinder with conical (round) ends set horizontally in a brick work. •Some of these boilers were 40 feet long. •The cylinder was half filled with water and a fire ignited in furnace at one end.

The Improved Heat Exchanger : The Cornish Boiler

Economics was the driving force behind new designs for HXs. Development of the Cornish Boiler was a step in that direction.Until that time designers had always placed the furnace beneath the water cylinder. Attempts to make use of the heat that was going up the chimney were limited to simply rapping the hot gasses around the boiler several times. A genius had the idea of putting the fire where it would do the most good, in with the water. Not actually "IN" the water but literally inside the cylinder containing the water.

The Next Heat Exchanger : The Lancashire Boiler

The need for smaller more powerful, to say nothing of safer, HXs finally led to the Lancashire Boiler design. Basically the same as the Cornish Boiler with its internal furnace design. The first advance was in the number of furnaces. Each boiler had two completely separate furnaces sitting side by side. And each furnace had a separate flue system. At first this might seem silly yet the idea behind having two separate fires going at the same time is outstanding.

Yet Another Heat Exchanger :The Upright Fire Tube Boilers

• So far in this short history of the HX we have looked at how the horizontal boiler developed.

• The term Fire Tube accurately describes the basis of HX.

• The water tank or boiler is a vertical tank not a horizontal cylinder as in the other boilers already described.

• Like the Cornish and Lancashire boilers the furnace is located inside the water tank.

• At the bottom of the tank where it is surrounded by water on all sides except the bottom.

• But take note, there are a number of brass tubes which extend through the boiler to the chimney.

• Depending on the individual manufacturer, there could be as many as 100 of these tubes.

Yet Another Heat Exchanger : The Scotch Boiler

• Engineers and designers of steam boilers had long understood the relationship between the amount of heat generated in a furnace and the ability of water to absorb that heat.

• Basically, the larger water surface exposed to the heat the more heat is transferred to the water.

• Like the Cornish and Lancashire boilers, the Scotch Boiler utilizes internal furnaces with the fire box and primary flue traversing the lower portion of the water cylinder.

• Yet unlike the Lancashire boiler, the Scotch boiler does not utilize Galloway tubes. Instead, the designers choose to manufacture the water tank from corrugated plates.

Course Admission Criteria

• Strong interest and/or need for a thermal design restricted elective

• Heat transfer, Fluid Mechanics and Thermodynamics are the prerequisite courses

Course Rules

• 1 MT exams and term projects

• Regular Homework Assignments

• Mathcad use required for some exams and Homework assignments

• Before the finals there will be a session for oral presentation of term projects

• 100% attendance is expected

Schedule and Grading

• Schedule: Tue 09:45 - 10:45, @ A101

Wed 09:45 - 10:45, @ A101

• Most lectures will be presented with PowerPoint some supplements on Black board.

• Grading: Exams: 75%

HWs and Design projects :25%

Design Problem

• Design problems will be selected in consultation with the instructor. Projects will be group design projects. The objective of the projects is to set the student to try to do a thermal design of a heat exchanger using the fundamentals of thermodynamics, fluid mechanics and heat transfer. There will be a written reports and an oral presentation.

Textbook

• “Heat Exchangers: Selection, Rating and Thermal Design, 2nd ed.” by Sadık Kakaç and Hongtan Liu, CRC Press 2002

• There are other books in the library that you can use as a reference (e.g. Handbooks of Heat Exchangers and Heat Transfer)

• CRC Handbook of Chemistry and Physics is a good reference for properties

Course outlineTopic Reading

Introduction (2 lectures) Chapter 1

Basic Design Methods (3) Chapter 2

Design Correlations (2) Chapter 3

Pressure Drop in Heat Exchangers (3) Chapter 4

Fouling of Heat Exchangers (3) Chapter 5

Double-Pipe Heat Exchangers (3) Chapter 6

Shell-and-tube Heat Exchangers (4) Chapter 8

Gasketed-Plate Heat Exchangers (4) Chapter 10

Compact Heat Exchangers (3) Chapter 9

Correlations for two-phase flow (3) Chapter 7

Condensers and Evaporators (4) Chapter 11

Steam Generators (2) Steam by B&W

Main Classification

• Recuperators / Regenerators

• Direct Contact / Transmural heat transfer

• Single / Two phase

• Geometry

Gasketed-plate heat exchanger