heat loss calculation

Czech Technical University in Prague

Department of Microenvironmental and Building Services Engineering

http://tzb.fsv.cvut.cz

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Heat loss calculation Standard CSN EN 12831 Method for calculation of the design heat load

Assignment 4 Design heating system in two variants. Design local heating system equipped with local boiler in your flat as first variant and central system for entire building as second variant.

Working steps:

1) Calculate total design heat load for all rooms in your flat at first floor. Use the simplified method from CSN EN 12831.

2) Calculate total heat losses of entire building. Use the envelope method.

3) Design of heat emitters in your flat according to results from step 1.

4) Prepare local heating system. Draw plan of the system. This is the first variant.

5) Calculate pressure drop of main branch. Design proper pump. Update plan of local heating system due to calculation results (dimensions).

6) Draw ground floor and first floor plans and section of central heating system. This is the second variant.

7) Design central boiler in the boiler room. Use results from envelope method (step 2).

8) Draw plan and scheme of boiler room.

9) Calculate expansion vessel and pressure relief valve.

10) Calculate heating and hot water annual energy consumption of the whole building.

TEXT PART

• Total design heat load calculation – all rooms in your flat (Heat loss-Example, tables) • Total heat loss calculation - whole building, simple envelope method • Heat emitters design – entire flat (Heat emitters design), (Heat emitters design-example) • Calculation of pressure drop of main branch in local heating system, design of pump

(variant 1). • Design of central boiler - variant 2. • Calculation of expansion vessel and pressure relief valve - variant 2. • Calculation of annual energy consumption - variant 2.

DRAWINGS

• Plan of your flat with local heating system – variant 1. (Heating system-flat_A , Heating system-flat_B)

• Plan of your flat with central energy source – variant 2 • Plan of ground floor with central heating system – variant 2 • Section of central heating system – variant 2 • Plan and section of boiler room – variant 2




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SIMPLE METHOD (residential buildings only) TOTAL DESIGN HEAT LOSS

DESIGN TRANSMISSION HEAT LOSS

θe….external air temperature (°C). Czech Republic -12, -15, -18°C

CSN 730540 Heat transfer coefficient (Czech national standard)

Heat transfer coefficient in buildings with outbalanced temperature 20°C (W/m2.K)

Construction description Required values

Recommended values

Flat roof, sloping roof to 45° Ceiling, floor above exterior

0,24 0,16

External wall, sloping roof over 45° wall adjacent to unheated attic

light 0,30 0,20 heavy 0,38 0,25

Floor / wall adjacent with earth 0,45 0,30 Internal wall heated to unheated space 0,60 0,40 Internal ceiling-temperature difference 10°C 1,05 0,7 Internal wall-temperature difference 10°C 1,3 0,9 Internal ceiling-temperature difference 5°C 2,2 1,45 Internal wall-temperature difference 5°C 2,7 1,8 Window, door in external wall-heated space to 1,7 1,2




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exterior Window in sloping wall to 45° 1,5 1,2

DESIGN VENTILATION HEAT LOSS

Note 1: If you have kitchen as a part of living room, consider air exchange 0.5 1/h.

Note 2: Bathroom air supply is usually from hall of flat, not from exterior, so design temperature

difference is (θint,BATH – θint,HALL) = (24 – 20)°C.




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TOTAL DESIGN HEAT LOAD

Residential building

Night setback max. 8h

TOTAL DESIGN HEAT LOAD FOR A BUILDING ENTITY OR A BUILDING




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EXAMPLE:




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INPUT DATA:




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HOBBY ROOM CALCULATION:




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Room name

Temperature data

Design external temperature qe °C

Design internal temperature qint,i °C

Design temperature difference qint,i-qe °C

Transmission heat losses

Code Building

element

fk Ak Uk fk·Ak·Uk

p.u. m2 W/m

2·K W/K

External wall 0,00

External wall 0,00

Window 0,00

Window 0,00

Internal wall 0,00

Internal wall 0,00

Internal wall 0,00

Door 0,00

Floor 0,00

Total transmission heat loss coefficient HT,i=Σk fk·Ak·Uk W/K 0,00

Total transmission heat loss FT,i=HT,i · (qint,i-qe) W 0

Ventilation heat losses

Internal volume Vi m3

Minimum air exchange rate nmin h-1

Total ventilation heat loss coefficient HV,i=0,34·Vi·nmin W/K 0,00

Total ventilation heat loss FV,i=HV,i · (qint,i-qe) W 0

Total ventilation and transmission heat loss FT,i+FV,i W 0

Correction factor for higher temperature fΔq p.u.

Design ventilation and transmission heat loss Fi=(FT,i+FV,i)·fΔq W 0

Heating-up capacity

Floor area A m2

Reheat factor fRH W/m2

Total heating-up capacity FRH,i=Ai·fRH W 0

Total design heat load FHL,i=Fi+FRH,i W 0

heat loss calculation

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