7. “আজর্কর পাঠ”
7.1ListtheSources of Heat Lossin
Winter Air Conditioning
7.2DescribetheTechnique of
Reducing Heat Loss in Winter
AirConditioning
PresentedBy:A.M.ATIQULLAH,INSTRUCTOR(Tech)RACDHAKAPOLYTECHNICINSTITUTE,TEJGAON,Dhaka
49. Heat Load or Heat Gain (হিেলগইি)
A Buildingor Room GainsHeat from ManySources
Inside Occupants, Computers, Copiers, Machinery,
andLightingallProduce Heat.WarmAirfromOutside
Enters Through Open Doors and Windows, or as
‘Leakage’ Though the Structure. However the Biggest
Source ofHeatisSolarRadiation fromtheSun, Beating
downon the Roof andWalls,andPouringThrough
the Windows, Heating Internal Surfaces.
50. The Sum of All These Heat Sources is
Know as the Heat Gain (or Heat Load) of
the Building, and is Expressed Either
in BTU (British Thermal Units) or Kw (Kilowatts)
For an Air Conditioner to Cool a Room
or Building its Output Must be Greater
Than the Heat Gain.
51. It is Important before Purchasing
an Air Conditioner that a Heat Load
Calculation isPerformed to Ensure
it is big Enough for the Intended Application
@
52. HeatLoadCalculations/ হিটিংল াডকযা কুর্ িিপ্রণা ীিঃ
Thereare Several Different Methodsof Calculating
the Heat Loadfor a Given Area: Quick Calculation for
Offices. For offices with Average Insulation and
L;ighting, 2/3 Occupants and 3/4 Personal Computers
and a Photocopier, the Following Calculations
will Suffice:
53. Heat Generated by Lighting By Calculatingthe
Heat Gain from Each Individual Item and
Adding them Together, an Accurate Heat
Load Figure can be Determined.
54. েু র্ের (ft) লক্ষর্ে,
Heat Load (BTU) = Length (ft.) x Width
(ft.) x Height (ft.) x 4
হমোর্রর (m)লক্ষর্ে,
Heat Load (BTU) = Length (m) x Width
(m) x Height (m) x 141
55. For Every Additional Occupant add 500 BTU
IfThere areanyAdditionalSignificantSources ofHeat,
or Instance Floor to Ceiling South Facing
Windows,or Equipmentthat ProducesLots of Heat,
the Above Method Will Under Estimate the Heat Load
In Which Case the Following Method Should be
Used Instead. A More Accurate Heat Load
Calculation for any Type of Room or Building
56. The Heat Gain of a Room or Building Depends on:
The Size of the Area Being Cooled
The Size and Position of Windows,
and Whether They Have Shading
The Number of Occupants
HeatGeneratedbyEquipmentandMachinery
57. Step One(1) ধ্াপবাপযোয়-১
Calculate the Area in Square Feet(ft2) of the
Space to be Cooled, and Multiply by 31.25
Area BTU = Length (ft.) x Width (ft.) x 31.25
Step Two(2) ধ্াপ বাপযোয়-২
Calculate the Heat Gain Through the
Windows. If the Windows Don’t have
Shading Multiply the Result by 1.4
58. North Window (BTU) উত্তর জািা ারজিয-১৬৪
=Area of North Facing Windows(m.sq)x164
South Window (BTU) দহক্ষণ জািা ারজিয-৮৬৮
=AreaofSouth Facing Windows(m.sq)x868
If No Shading, North Window BTU
= North Window BTU x 1.4 লকার্িালিডিাথাকর্ -১.৪
59. If No Shading, South Window BTU
=South Window BTU x 1.4
Add the Results Together.
Total Window BTU =
(North Window + South Window)
Step Three(3) ধ্াপবাপযোয়-৩(হপপ ল াড)
60. Calculate the Heat Generated by Occupants, Allow
600 BTU Per Person.
Occupant BTU = Number of People x 600
Step Four(4) ধ্াপবা পযোয়-৪ (ইকুইপর্মন্ট ল াড)
Calculate the Heat Generated by Each Item of
Machinery - Copiers, Computers, Ovens etc.
Find the Power in Watts for Each Item, Add Them
Together and Multiply by 3.4
Equipment BTU = Total Equipment Watts x 3.4
61. Step Five(5) ধ্াপ বা পযোয়-৫
Calculate the Heat Generated by Lighting.
Find the Total Wattage for All Lighting and
Multiply by 4.25
Lighting BTU = Total Lighting Watts x 4.25
Step Six(6) ধ্াপ বা পযোয়-৬
Addthe AboveTogether to Findthe Total Heat Load
Total Heat Load BTU = (Area BTU + Total Window
BTU + Occupant BTU + Equipment BTU + Lighting
BTU)
62. Step Seven(7) ধ্াপবাপযোয়-৭
Divide the Heat Load by the Cooling
Capacity of the Air Conditioning Unit
in BTU, to Determine how Many Air
Conditioners are Needed.
Number of a/c Units Required = Total
Heat Load BTU / Cooling Capacity BTU
