#5 Heat Exchanger

Question 1

Cooler Examples

Answer 1

Jacket CW cooler, lubricating cooler,steam condenser

Question 2

Heater Examples

Answer 2

Fuel oil heater, lubricating oil heater, evaporator

Question 3

Baffles

Answer 3

plates that are introduced between the tube end plates

support the tubes
increase dweel time
increase contact area for heat transfer

Question 4

dwell time

Answer 4

directing the flow causes the hot fluid to stay longer inside the tube stack, increasing the duration for heat transfer as well as efficiency of the cooler

Question 5

Materials of a shell & Tube Type heat exchanger
Tubes:
Tube plates:
Shell & water boxes:
Baffles:

Answer 5

Tubes: Aluminum brass, or Cuprous Nickel
Tube plates: Cast naval brass (alloy of copper, zinc and tin)
Shell & water boxes: Cast iron, gunmetal (alloy of copper, zinc and tin)
Baffles: Copper, rolled naval brass

Question 6

Cleaning and Inspection

Answer 6

lose efficiency through accumulation of deposite like marine growth, sludge, mud, sand

Such deposits increase the thickness of the tubes thus affecting heat transfer. This causes greater temperature difference between the hot and cold surfaces and results in high thermal stress on the tubes.

Tubes can be cleaned mechanically or chemically.

Question 7

Corrosion Protection

Answer 7

1. Inserting sacrificial anodes on the water boxes. Some metals corrode and form a protective layer on other metals (example soft iron, mild steel, zinc). This property allows them to be made into ‘sacrificial’ pieces so that no corrosion will take place on the tubes, baffles and shells.
2. Water boxes coated with rubber Eastover, bitumen or epoxy resin. Corrosion will be minimised.
3. Dosing the system with 10% of ferrous sulphate on the fresh water side. The
   chemical concentration will inhibit marine growths.

Question 8

Plate Heat Exchangers

Answer 8

The Frame consists of a front Frame
Plate with 2 carrier bars. The Frame Plate has inlet and outlet connections for both the coolant and fluid. Plates are guided and supported by the carrier bars. The plate stack is clamped tight by tie bolts
Each plate is about 0.6 mm to 0.8 mm thick and has four distribution holes. It is corrugated to increase strength and surface area of the plate. Greater surface area also meant better heat transfer. Corrugation also creates turbulence in the flow, increasing heat transfer efficiency and prevent deposits from forming on the plates

Question 9

Rubber Seals

Answer 9

Rubber seals are placed in each of the distribution holes as well as around the corrugations.
The rubber seals and rings are only placed on one side of the plate. The ‘back-side’ of the same plate has no seal but another plate with seals will be placed on it. When the plates are clamped together, it is these rubber seals and rings that prevent the liquid from leaking out.