KeyWarm Blog

Case example:

1. Design conditions:

The length, width and height of the drying room are 16m, 6m, and 4.6m respectively; the surrounding of the drying room is made of rock wool sandwich panels, and the roof is made of rock wool board ceiling; the minimum outdoor temperature in winter is 0°C.

2. Design requirements

The overall time for high-temperature disinfection of vehicles is 40 minutes, the time required to heat up to 70 °C is controlled within 10 minutes, and the temperature above 70 °C is maintained for 30 minutes.

3. Equipment selection
3.1 Heater selection: the minimum outdoor temperature is 0°C, and the indoor temperature is required to be 70°C, then the overall temperature rise is 70°C; the room space volume is 16*6*4.6=441.6m³, and the thermal insulation coefficient is 2.7 (this coefficient is conservative considering the heating and heat absorption of the wet vehicle itself), the required heat load = 441.6*70*2.7=83kW, that is, the heating space needs 83kW of heat per hour, and the designed heating time is 10 minutes, then the required heat load is 83*60÷ 10=498kW, the heat load of each equipment is 80kW, then 498÷80=6.225, it is recommended to choose 6 sets of 80kW equipment.
3.2 Heat recovery Ventilator selection: In order to shorten the drying time, it is necessary to discharge the air with high temperature and high humidity to the outside; considering the large temperature difference between indoor and outdoor, heat recovery ventilators needs to be added to solve the contradiction between dehumidification and energy consumption. After calculation, two 2,500m³/h heat recovery devices and six 80kW heaters were selected to match.
3.3 Rear exhaust fan selection: In order to dry the inside of a closed vehicle, four 36″ high-temperature explosion-proof fans are specially selected and installed at the rear of the vehicle to blow air into the vehicle for heating and drying.

Typical Layout of ASF Disinfection Drying Station

To select an air curtain the following factors should be kept in mind:

• The height of the installation measured from the discharge diffuser to the floor
• The width of the door
• The location of the building to determine the level of protection needed against weather conditions (temperature, humidity and wind)
• If the building has several doors in the same area, different or opposite façade
• If the building has several storeys connected by escalators/stairs
• Pressure differences between the inside and outside of the building
• Door compatibility: Always open, automatic open, manual open, revolving door, etc.
• Characteristics of the ventilation and air conditioning installation
• Voltage and electrical power availability
• Type of business, style and decoration of the premises
• Free hanging or recessed, horizontal or vertical installation, heated or unheated, etc.

The information within this section has been designed as a ‘quick check’ for non-technical
stakeholders to confirm that their air curtains have been installed in an appropriate and functional
way. These checks are not comprehensive and should not replace the manufacturer’s installation
instructions.

HOW FAR IS THE AIR CURTAIN FROM THE DOOR HORIZONTALLY?

An air curtain should be installed close enough to the opening to prevent heat loss from cold air entering the space or vice versa for cold room applications. As shown in the diagram below, in an ideal installation, there would be no separation horizontally between the opening and the air curtain. However, the air curtain can still be effective provided the separation is within 50 cm.

HOW FAR AWAY IS THE AIR CURTAIN FROM THE DOOR VERTICALLY?

Ideally, the outlet of an air curtain is installed directly above the opening it is designed to protect.
If an air curtain is installed too far above the opening, the result will be one of the following
two outcomes: the air curtain may not be fully effective or a larger more powerful unit may be
required. Both these outcomes are a consequence of the energy required to create and maintain
the jet of air across the opening. As a general check, unless the additional height has been taken
into consideration, a vertical separation of up to 50 cm is acceptable

DOES THE AIR CURTAIN COVER THE ENTIRE WIDTH OF THE DOOR OPENING?

In an appropriate installation, the stream of air generated by the air curtain should cover the entire
opening it has been installed to protect. If the air curtain is oversized, it will use additional energy
without providing any additional benefit to the consumer. If the air curtain is undersized, it cannot
create an air stream large enough to fully protect the opening it has been installed above, leading
to increase space heating or cooling costs as a result of infiltration.

Heating Power (Recommendation only): 

Minimum heating power(kW)=Poultry house volume(m³)*0.07kW/m³

Considering small temperature difference in a poultry house, a typical 100m*12m broiler house needs 400kW thermal input or 4 sets of KWIH100 heaters while 120m*12m broiler house needs 6 sets of KWIH100 heaters.

Here are some criteria to consider in installing the units:

• Installation height;
• Positioning;
• Warm air circulation;
• Venting: combustion products are usually vented outdoors.

                                       Typical layout of KWIH heaters in a broiler house

Heating Power: 

• Warehouse: 80-110 W/㎡
• Factory: 120-180 W/㎡

• Pig House: Volume(m³)*0.04(kW/m³)

• Poultry House: Volume(m³)*0.07(kW/m³)

Combustion: Sealed combustion (the combustion air is taken directly from the space to be heated or from outside).

Venting: The combustion products can be vented indoors or outside.

• Minimum height to be respected, according to each manufacturer.
• Installation is not recommended in places where there are chlorine products, solvents or explosives, but certain models are suitable for that type of environment.
• The combustion products are vented indoors with additional ventilation. Usually, this calls for an interlock between the appliance and a mechanical extractor fan. A fresh air supply unit needs to be installed in order to maintain an acceptable level of CO2 (5,000 ppm). For more details, consult the manufacturer’s Installation Guide.
• The ventilation rate stipulated in Code B 149.2 is 300 ft3 of air per minute per 100,000 Btu/hr or each kW per 22m³/h fresh air of low intensity infrared installed.

Heating Power: 

• Warehouse: 80-110 W/sqm
• Factory: 120-180 W/sqm

Combustion: Sealed combustion (the combustion air is taken directly from outside but mostly from the space to be heated)

Venting: The combustion products can be vented indoors or outside but mostly outside for multiple burner system.

• Minimum height to be respected, according to each manufacturer.
• Installation is not recommended in places where there are chlorine products, solvents or explosives, but certain models are suitable for that type of environment.
• The combustion products are vented indoors with additional ventilation. Usually, this calls for an interlock between the appliance and a mechanical extractor fan. A fresh air supply unit needs to be installed in order to maintain an acceptable level of CO2 (5,000 ppm). For more details, consult the manufacturer’s Installation Guide.
• The ventilation rate stipulated in Code B 149.2 is 300 ft3 of air per minute per 100,000 Btu/hr or each kW per 22m³/h fresh air of high intensity infrared installed.

Select the number of heat exchangers at the maximum load to meet the minimum ventilation for Stage 1 and/or Stage 2. For all-in, all-out livestock houses, this varies as the animals grow. Determine the number of heat exchangers (maximum airflow) by adult animals and run the appropriate number of heat exchangers (reduced airflow) for young animals.

The biggest challenge facing heat exchanger application in a poultry house is the amount of dust
encountered in the air. Dust in the exhaust airstream, if not handled properly, will degrade the
performance of any heat recovery system. Proper handling of dust is critical to the success of a heat
recovery system application. Traditional flat­plate heat exchangers require upstream filtration systems
on the warm exhaust air side to intercept the dust (from indoor air) before it enters the heat exchangers.
After a grow­out, exchanger cores need be cleaned using compressed air or water, depending on the
equipment designs. Regular cleaning effectively removes dust and rejuvenates the cores.

• Heating power of pig house(kW)=volume(m³)*0.04kW/m³
• Heating power of poultry house(kW)=volume(m³)*0.07kW/m³
• The temperature in a house with a well-designed forced-air space heating system is relatively uniform from floor to ceiling and around the house. Poultry houses and pig houses commonly are rated 30kW to 70kW. The industry standard is to provide around six to eight heaters in a 120 long broiler house, rather than four large heaters. This improves heat distribution in the house.
• Large heaters are only marginally more expensive than units with half the kW capacity, so it is common to over-design for houses that will contain brooding chicks. 

• Space heaters operate at low gas supply pressures. Heated air is distributed with the heater fan and through mixing with the incoming ventilation air jet. Maintaining warm temperatures near the floor during early brooding is a common problem with space heaters.
• Broiler management guidelines recommend starting air temperatures of 32–35°C at day 1. Every day thereafter, the guidelines recommend decreasing air temperature incrementally until a final temperature of 19–21°C is reached at around day 27 and maintained for the remainder of the growout.

• Most space heaters use interior air and are unvented, which means they exhaust carbon dioxide, moisture, and incomplete combustion products directly into the building. Approximately 1.7 kg of water vapor is produced per kg of propane gas combusted. Thus, to prevent moisture accumulation caused by unvented heaters, it is recommended that minimum ventilation rate be increased by 14.5m³/h per kW heater capacity.
• Stir fans are commonly installed near the ceiling to circulate this hot air back to the litter where it is useful to chicks. In some instances where adequate temperatures cannot be maintained, both space and radiant heat systems are used.
• Thermostat location is important to maintain uniform temperature and energy savings.

• Heating power of pig house(kW)=volume(m³)*0.04kW/m³
• Heating power of poultry house(kW)=volume(m³)*0.07kW/m³
• The temperature in a house with a well-designed forced-air space heating system is relatively uniform from floor to ceiling and around the house. Poultry houses and pig houses commonly are rated 30kW to 70kW. The industry standard is to provide around six to eight heaters in a 120 long broiler house, rather than four large heaters. This improves heat distribution in the house.
• Large heaters are only marginally more expensive than units with half the kW capacity, so it is common to over-design for houses that will contain brooding chicks. 

• Space heaters operate at low gas supply pressures. Heated air is distributed with the heater fan and through mixing with the incoming ventilation air jet. Maintaining warm temperatures near the floor during early brooding is a common problem with space heaters.
• Broiler management guidelines recommend starting air temperatures of 32–35°C at day 1. Every day thereafter, the guidelines recommend decreasing air temperature incrementally until a final temperature of 19–21°C is reached at around day 27 and maintained for the remainder of the growout.
•  

Heating Area Volume & Climate Zone

The required kW output required is primarily dependent upon the area to be heater and the climate zone in which you live.  

The following rough guide assumes your ceilings are no higher than 2.4M:

Very Cold Zone: 1kW output required for each 8.5m²

Cold Zone: 1 kW output required for each 10m²

Cool Zone: 1kW output required for each 13 m²

Mild Zone: 1kW output required for each 16m²

Adjustment Factors

The indicated gas heating areas would be adjusted down by 5% for each of the following conditions: house built on pillars (non-slab), no carpets on floors, no drapes on windows or a ceiling height exceeding 2.4m. Deduct an additional 10% if the area does not have ceiling insulation. Please note that this is only a guide and individual home designs and situations may vary.

Gas Heater Sizing Example #1: 

You live in the Cold Zone and you want to heat an area 5m X 10m, which equals 50m².

Because 1kW will heat 10m², you should need a heater with a 5kW output.

Gas Heater Sizing Example #2: 

Same as the previous example but in this case your ceilings are over 2.4m and you have wood flooring instead of carpeting.                            You would need to deduct 5% for each of these two items. So, instead of 1 kW heating 10m², it would heat 9m² (10% total reduction). This means you would need a heater with 5.6 kW of output (50 ÷ 9).

• The minimum clearance between the room heater and the combustibles must meet the manufacturer’s requirements
• Reserve enough space for maintenance
• The exhaust pipe is inclined downward by minimum 3°
• The outdoor part of the exhaust pipe is kept away from combustibles and cannot be covered or shaded by snow
• When installing on the wall, the bottom of the heater is 200-500mm away from the ground
• Gas leaking alarm and emergency gas shut-off valve are highly recommended.