TR EN

HEAT LOSS CALCULATION and INSTALLATION CALCULATIONS

APPROXIMATE HEAT LOSS CALCULATION AND SELECTION OF SYSTEM COMPONENTS

HEAT LOSS CALCULATION:

Through engineering:

Through this method, heat loss calculation sheet, radiator and detail calculation sheet, loss values calculation sheet and pipe calculation sheet are filled separately for each environment during heat loss calculation.

In heat loss calculation sheet, calculations are made by considering direction of the volume for which heat loss calculation is made, wall-flooring thicknesses and external wall-flooring-window areas.  Radiator and detail calculation sheet is used during selection of radiators and placement on architectural project after the heat loss of volume is calculated.  In loss (specific resistance) values table, losses, which make water flow difficult in pipes, S parts, brackets, separations etc., and cause pressure loss.  In pipe calculation sheet, each pipe piece within the system is numbered, and the sheet is filled with parameters such as amounts of heat passing through each piece, length, speed and coefficient of friction.

Approximate method:

Volumes to be heated have m3 based approximate calculation values in terms of annual average temperatures.

For 3 oC:

 

Insulation protected

Kcal/hm3

Insulated free

Kcal/hm3

Uninsulated protected

Kcal/hm3

Uninsulated free

Kcal/hm3

Penthouse

19

28

30

40

Mezzanine

17

25

26

35

Basement

19

28

30

40

For -3 oC:

 

Insulation protected

Kcal/hm3

Insulated free

Kcal/hm3

Uninsulated protected

Kcal/hm3

Uninsulated free

Kcal/hm3

Penthouse

22

30

40

50

Mezzanine

20

28

32

40

Basement

22

30

35

45

For -6 oC:

 

Insulation protected

Kcal/hm3

Insulated free

Kcal/hm3

Uninsulated protected

Kcal/hm3

Uninsulated free

Kcal/hm3

Penthouse

25

33

45

55

Mezzanine

22

30

35

43

Basement

25

33

40

50

For -12 oC:

 

Insulation protected

Kcal/hm3

Insulated free

Kcal/hm3

Uninsulated protected

Kcal/hm3

Uninsulated free

Kcal/hm3

Penthouse

28

38

50

60

Mezzanine

24

34

38

46

Basement

28

38

44

54

For -21 oC:

 

Insulation protected

Kcal/hm3

Insulated free

Kcal/hm3

Uninsulated protected

Kcal/hm3

Uninsulated free

Kcal/hm3

Penthouse

35

45

60

70

Mezzanine

30

40

44

55

Basement

35

45

53

63

 

Approximate heat loss of the desired volume can be calculated through help of these tables.  Boiler is selected according to the heat loss value calculated.

For example, approximate heat loss of a 20 m² uninsulated-protected room with roof height of 3 meters located in mezzanine is:

20x3x32= 1,920 kcal/h.

In the same way, approximate heat loss for 150 m² house is:

150x3x32= 14,400 kcal/h.

Heating device is selected according to the heat loss value found.  E.g. conventional combi boiler, condensing combi boiler and central heating should individual heating be performed, while central boiler should central system heating be performed.

BURNER CAPACITY CALCULATION:

Should blow system boiler is to be used; calculation of burner compatible with boiler capacity is made with the following formula:

Qk

BBr =

HBr

 

BBr : Burner capacity (kg/h)

Q: Boiler capacity (kcal/h)

Br : Burner efficiency (checked from catalogue)

H: Fuel lower heating value (kcal/h)

 

Hvalues:

Diesel: 10200 kcal/kg

Fuel oil number 4: 10100 kcal/kg

LPG: 11800 kcal/kg

Natural gas: 8250 kcal/m3

Zonguldak pit coal: 7000 kcal/kg

Coke: 6000 kcal/kg

Lignite coal: 2000 – 5500 kcal/kg

 

Approximate Br values:

Lignite coal: 0.65

Coke and pit coal: 0.72

Fuel oil: 0.82

Natural gas: 0.92

 

PIPE DIMENSION CALCULATION:

While pipe dimension are calculated, water speed at the lowest value in branches must increase as the pipe dimension increases, and reach the highest speed at boiler entrance. However, water speed must not be higher than 0.2-0.3 m/sec in 90 oC/70 oC hot water heating systems, 1 m/sec. in pipes up to 2”, and 1.5 m/sec. in larger pipes.  Later, straight pipe and local pressure losses are calculated and pump is selected for the system.

SELECTION OF RADIATOR VALVES:

You must decide whether to use radiator valves with inner adjusted flow rate, or thermostatic radiator valves (TRV).  In case of TRV, you will prevent the volumes to heat up beyond the desired temperature and ensure fuel saving (each further heating by 1°C means extra fuel spending by 5%), and obtain comfort conditions easier and make them permanent.

Thermostatic radiator valve

RADIATOR SELECTION AND PLACEMENT:

Panel or iron cast radiators are selected from relate catalogues according to the heat loss value calculated for volume.  Cast iron radiators have number of sections, while panel radiators have radiator length.  Location with the most heat loss (such as window bottoms) is selected for placement.  However, you must pay attention to the fact that these values calculated are from radiators with open surrounding.  In case part of radiators is to stay in closed position (placing marble on radiator, placing radiator inside niche or mesh box etc.), additions are made to the calculated values.  In that case, radiator thermal performance may drop down to 80%.  Radiators must be placed on floor as much as possible.  For ideal placement, 4 cm wall space and 6 cm ground clearance is sufficient.

In iron cast radiators with more than 20 sections and panel radiators longer than 1.5 m, return branch must be taken from the other end (cross connection) of the radiator.

Important note: In practice, no system operates at 90 oC/70 oC. Since they operate at 75 oC/65 oC, you must ask manufacturers the heat value table of radiators by 75 oC/65 oC system.

SELECTION OF CIRCULATION PUMP

Circulation pump flow rate is detected with the amount of water circulating in the installation.  The water circulating in the installation is dependent on the total heat requirement of the installation and forward-return temperature of water.

Qk

Q=

C.p.(tg-td)

 

Q: Pump flow rate (m3/h)

Q: Heat requirement (kcal/h)

C : Specific heat of water (1 kcal/kgoC)

p : Water density (approximately 970 kg/mfor 90 oC/ 70 oC systems)

t: Forward water temperature

t: Return water temperature

However, this expression is not used in heater types since thermal power is detected according to the flow rate.  In this case, suggestions of the heater manufacturer are taken for pump flow rate.

Circulation pump pressure: Circulation pump pressure must be greater than coefficient of friction of the column, which has the highest friction losses and is called critic circuit.

H> ∑R.L + ∑Z mmSS

R.L: Straight pipe losses:

Z: Local losses

Pressure value found is increased if boiler room losses are considered in calculations. Should boiler room losses not be considered,  300-800 mmSS is added to the calculated value.

Circulation pump is desired to operate in the middle of the flow rate in abscissa (horizontal axis) and the pressure characteristic curve in ordinate (vertical axis).  There is a spare part in case of failure.

Pumps are normally connected to the return line.  Should the installation have big capacity, centrifugal pump, which is used instead of the circulation pump, is connected to the outlet line.  Thus, no critical point to form air is left in the system.

EXPANSION TANK CALCULATION:

Closed expansion tank:

Its greatest feature is that it blocks the penetration of the oxygen in air into the system water and prevents corrosion.  Moreover, contrary to open expansion containers, the water does not vaporize and causes both water and heat loss.  They are manufactured in cylindrical, spherical, flat round and flat rectangular forms and placed in boiler rooms.  Thus, placement and freezing problems are eliminated.  The system must definitely have safety valve and manometer.

Closed expansion tanks are suitable only for automatic controlled combustion (liquid and gas fuel) boilers.  It must not be used in hand loading coal boilers since it may cause big heat fluctuations.

It has 6, 12 and 18 liter models for room heaters depending on heating capacity.

As practical calculation, 6% of the system water volume is taken as closed expansion tank volume.

The following method can be followed in order to find the water volume in the installation practically:

600 mm high PKKP model panel radiators are used mainly in the market.  1 meter of this radiators takes almost 6 liters of water.  Suppose a total of 100 meter 600 PKKP radiator is used in an apartment heated with central boiler.  In this case, the total water volume in radiators is:

100x6=600 liters.

Now suppose this water volume is 1000 liters when we add the approximate amount of water in the installation and boiler by looking at the catalogue value.

In this case, expansion tank volume required for the system is:

1.000x0.06=60 liters.

Open expansion tank:

They are used in solid fuel systems since there is no flame control possibility.  Water temperature does not exceed 100 oC since the system pressure does not exceed 1 bar.  New water must be added to the system since the water in contact with the atmosphere will vaporize.  Oxygen within recently added water causes corrosion. The important point is that forward and return safety pipes have not shut-off valve.  Safety pipes are forward and return safety pipes that transmit the amount of heating water, which has increased in terms of volume due to temperature difference, increase of temperature in particular, in heat producer, i.e. boiler and installation, to the expansion depot.  Forward pipe must be connected from top, while return safety pipe must be connected from the bottom. In this case, water will flow from the forward safety pipe into the expansion depot if the water pump pressure is larger than the required value.  Since such flow is undesired, either a pump with less pressure must be connected to the system, or water flow into expansion depot must be prevented by adjusting the by-pass valve in the pump station.

Normal water level in the installation is when the water is 90oC and the expansion depot is full. Water level is read in mSS (meter water column) from the hydrometer attached on the boiler or collector.

Message tube, which is connected to the expansion depot from minimum water level and laid until boiler room and attached a valve (1/2”) on its tip, helps you to check whether there is enough water in the installation.

Forward and return safety pipes cannot be smaller than 1”’. Expansion tanks are included in the scope of TS 713.

Open expansion tank volume calculation is made in the same manner as in closed expansion tank volume calculation.