Boilers

Question 1

Classification of boilers : 5 variables

Answer 1

Pressure
Materials
Heating Modes
Heat Recovery
Fuels

Question 2

2 types of pressure

Answer 2

low (160 psig)

Question 3

2 types of materials

Answer 3

cast iron boilers

steel boilers

Question 4

2 types of heat recovery

Answer 4

Condensing boilers

Non condensing boilers

Question 5

3 types of fuel

Answer 5

Natural Gas
Oil
Electricity

Question 6

2 types of boilers

Answer 6

fire-tube

water-tube

Question 7

Boiler selection parameters

Answer 7

• ASME code certification
• Net boiler output
• Operational efficiency
• Auxiliary power req
• Space req
• Combustion air + venting req
• Water treatment req
• Cleaning provisions for heat transfer surfaces
• Operational safety req

Question 8

Water treatment for boilers

Answer 8

• sodium ions
• sodium nitrate
• de-aereation of feed-water
• boiler blow down
• recommended Ph

Question 9

What is the purpose of sodium ions in boilers?

Answer 9

Neutralize calcium deposits/scale

Question 10

What is the purpose of sodium nitrate in boilers?

Answer 10

Inhibit growth of corrosion

Question 11

Difference b/n steady state and seasonal efficiency?

Answer 11

• • steady state : full load conditions
• • seasonal : based on actual operation conditions. includes full and partial loads

seasonal efficiency

Question 12

what is the ashrae method for combustion efficiency?

Answer 12

x : net flue temperature rise
y : flue gas losses, percent

lines represent the O_2 concentration

Question 13

what are the 6 types of energy leaving the boiler system?

Answer 13

1. useful heat
2. sensible heat loss in dry glue gases
3. heat loss inw ater vapour formed bu combustion of hydrogen in the fuel
4. heat lossin water vapour in combustion air
5. heat loss from incomplete combustion
6. heat loss from unburnt carbon in the fuel

Question 14

which heat losses are negligible and why?

Answer 14

heat loss from incomplete combustion (clean combustion equipment(

heat loss from unburnt carbon in the fuel (negligible for gas and oil fuels)

Question 15

3 types of heat distribution terminals

Answer 15

• baseboard heaters
• convectors
• cast iron radiators

Question 16

Steps for hot water heating system design

Answer 16

1. determine room by room design day heating loads
2. choose a piping circuit layout
3. select terminal heater sizes and number of units per room
4. locate terminal units on exterior walls under the windows
5. use pipe fittings and allow for pipe expansion
6. determine the pipe diameters for each section
7. calculate total friction losses in the system
8. select pump
9. size of boiler = design day building heat load + 15%

Question 17

3 types of combustion air and venting requirements

Answer 17

• Natural draft boilers
• Forced draft boilers
• Induced draft boilers

Question 18

what is npsha

Answer 18

net positive suction characteristics of pumps

Question 19

describe flat curves for pump characteristics

Answer 19

useful in closed loop systems where flow rate varies while the pump head is maintained constant

Question 20

describe steep curve for pump characteristics

Answer 20

installed in open loop systems (cooling towers) where constant flow is required at higher pressure heads