heater air design

8/13/2019 Heater Air Design

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3 Heating Load CalculationThe heat loss is divided into two groups:(i) the heat transmission losses through the confining walls, floor, ceiling, glass, orother surfaces, and(ii) the infiltration losses through cracks and openings, or heat required to warm

outdoor air used for ventilation.As a basis for design, the most unfavourable but economical combination of

temperature and wind speed is chosen. The wind speed has great effect on highinfiltration loss and on outside surface resistance in conduction heat transfer.

Normally, the heating load is estimated for winter design temperature usuallyoccurring at night, therefore, internal heat gain is neglected except for theaters,assembly halls, industrial plant and commercial buildings. Internal heat gain is thesensible and latent heat emitted within an internal space by the occupants, lighting,

electric motors, electronic equipment, etc.

3.1 Heat Transmission LossHeat loss by conduction and convection heat transfer through any surface is given

by:

(2)where Q = heat transfer through walls, roof, glass, etc.A = surface areasU = air-to-air heat transfer coefficientTi = indoor air temperatureTo = outdoor air temperatureHeat transfer through basement walls and floors to the ground depends on:(i) difference between room air temperature and ground temperature/outdoor air

temperature,


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(ii) materials of walls and floor of the basement, and(iii) conductivity of the surrounding earth.These portion of heat transmission is neglected in Hong Kong because of the factthat the weather in winter is not so severe and the values are very small in

comparison with other forms of heat transmission.

3.2 Infiltration and Ventilation LossThe heat loss due to infiltration and controlled natural ventilation is divided intosensible and latent losses.

3.2.1 Sensible Heat Loss, QsbThe energy associated with having to raise the temperature of infiltrating or

ventilating air up to indoor air temperature is the sensible heat loss which isestimated by:

(3)where r = air densityV = volumetric air flow rateCpa = specific heat capacity of air at constant pressureTi = indoor air temperatureTo = outdoor air temperature

3.2.2 Latent Heat Loss, QlaThe energy quantity associated with net loss of moisture from the space is latent

heat loss which is given by:


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(4)where r = air densityV = volumetric air flow ratewi = humidity ratio of indoor airwo = humidity ratio of outdoor airhfg = latent heat of evaporation at indoor air temperature

2 Design ConditionsIn principle, the heating and cooling loads are calculated to maintain the indoordesign conditions when the outdoor weather data do not exceed the design values.

2.1 Outdoor Design ConditionsIt is not economical to choose either the annual maximum or annual minimumvalues of the outdoor weather data in determining the outdoor conditions. The

outdoor design data is usually determined according to the statistical analysis ofthe weather data so that 1 to 5% of the total possible operating hours is equalled or

exceeded the outdoor design values.

2.1.1 Summer Design ConditionThe recommended summer design and coincident wet bulb temperature, when

chosen as being equalled to or exceeded by 2.5% of the total number of hours (i.e.2928 hours) in June, July, August and September, are(i) 23 oC dry bulb temperature, and(ii) 28 oC wet bulb temperature


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Figure 2 shows the outdoor dry bulb temperature and wet bulb temperature curves

for a typically hot summer day in Hong Kong. Usually the maximum temperature

of 33 oC occurs at 2 p.m. and the minimum temperature of 28 oC occurs justbefore sunrise. The daily range of dry bulb temperature is about 5 to 6 oC, and the

daily mean dry bulb temperature is 30.5 oC.

2.1.2 Winter Design ConditionThe recommended winter design and coincident relative humidity, when chosen as

being equalled to or exceeded by 1% or 2.5% of the total number of hours (i.e.

2160 hours) in December, January and February, are(i) 9 oC dry bulb temperature, and


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(ii) 50% relative humidityMinimum temperature occurs at 6 a.m. or 7 a.m. before sunrise and the daily rangeis about 6 to 8 oC during very cold winter days.

2.2 Indoor Design ConditionsFor most of the comfort air-conditioning systems used in the commercial and

public buildings, the recommended indoor temperature and relative humidity are as

follows:(i) Summer: 23.5 - 25.5 oC dry bulb temperature, 40 - 60 % relative humidity(ii) Winter: 21 - 23.5 oC dry bulb temperature, 20 - 30 % relative humidity

Head office :Jl. Daan Mogot no.119 Bl. A-6

JAKARTA BARAT 11510

Phone: 021-5663949, 021-5604314Fax: 021-56639210E-mail:

[email protected]

Branch Office:Jl Rungkut Mapan Tengah V Bl DD/7

SURABAYAPhone : 031-8712411, 031-8706485-6

Fax : 031-8704996
mailto:[email protected]:[email protected]:[email protected]


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Factory :Jl Semanan II 2

RT 008/07Komp. Industri Semanan, Kalideres

JAKARTA 11850Phone : 021-54398341, 021-54398342

Quick Details

Type: Aluminum heater grill roaster Power

Source:

Electric

Brand

Name:

Chinayu Model

Number:

CY-0000117

weight: 0.95kg power: 1800-3450WPackaging & Delivery

Packaging

Detail:

carton box,or as required

Delivery

Detail:

35days after place the order

Specifications

aluminum die heater

1.heating elemednt:1pcs

2.Temperature can reach 250 degrees

3.Using low pressure casting

4.290x170x26mm


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aluminum die heater

1.heating elemednt:1pcs2.Temperature can reach 250 degrees

3.Using low pressure casting

4.size:290x170x26mm

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Temperature, Dewpoint, and Humidity

ConversionsThe old saying goes, "It's not the heat, it's the humidity". The way the human body reacts to

warm temperatures is a function of both the actual temperature, and the moisture in the air.Low humidity lets the body cool off due to evaporation of perspiration. As the humidity rises,

less perspiration evaporates, and it becomes more difficult to dissipate the heat.

The heat index is an attempt to measure the apparent temperature, or the way it feels outside.

It uses a formula of both actual temperature, and absolute humidity. Generally, when the heat

index rises above 90 degrees, people should avoid being outside for too long, and when the

heat index is 105 degrees or higher, it's becoming dangerous. Note that the heat index is

calculated as an 'in the shade' temperature, so if you are in the sun, it could actually feel

warmer than the heat index indicates.

Another way to measure how hot it feels outside is to use the dew point temperature. The dewpoint temperature is an indicator of the absolute humidityif the temperature drops to the

dewpoint temperature, water vapor condenses to dew. No matter what the actual outside

temperature is, most people begin to feel uncomfortable when the dew point approaches 70

degrees, and dewpoints above 70 degrees are opressive.

The table below shows the heat index and dew points for differing combinations of air

temperature and relative humidity. To determine the heat index (and corresponding dew

point), locate the column with the air temperature, and match it with the approprite row for

humidity. For example, if it's 90 degrees and 55% relative humidity, the heat index is 97

degrees, and the dew point is 72 degrees. You'll likely feel uncomfortable. On the other hand,

if it's 90, but the relative humidity is 30%, the heat index is only 88, and the dew point is 54.

Most people wouldn't find this oppressive.

Keep in mind that different people react to heat and humidity differently, and that there is a

real danger when you spend too much time outside during a heat wave.

80 82 84 86 88

HI DP HI DP HI DP HI DP HI DP

10% 78 18 80 20 81 22 83 23 84 25


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20% 79 35 80 37 84 39 83 40 85 42

30% 79 46 80 48 82 49 84 51 86 53

40% 80 54 81 55 84 57 87 59 89 61

45% 80 57 82 59 84 60 87 62 89 64

50% 81 60 83 62 85 63 88 65 91 67

55% 81 62 84 64 86 66 89 68 93 70

60% 82 65 84 67 88 69 91 70 95 72

65% 82 67 85 69 89 71 93 73 98 75

70% 83 69 86 71 90 73 95 75 100 77

75% 84 71 88 73 92 75 97 77 103 79

80% 84 73 89 75 94 77 100 79 106 81

85% 85 75 90 77 96 79 102 81 110 83

90% 86 77 91 79 98 81 105 83 113 85

95% 86 78 93 80 100 82 108 84 117 86

100% 87 80 95 82 103 84 112 86 121 88

90 92 94 96 98

HI DP HI DP HI DP HI DP HI DP

10% 86 26 88 28 89 29 91 31 93 32

20% 86 44 88 45 90 47 93 48 95 50

30% 88 54 90 56 93 58 96 60 99 61

40% 93 62 94 64 97 66 101 68 105 70

45% 93 66 96 68 100 69 104 71 109 73

50% 95 69 99 71 103 73 108 74 113 76

55% 97 72 101 74 106 75 112 77 117 79

60% 100 74 105 76 110 78 116 80 123 82

65% 103 77 108 79 114 80 121 82 128 84


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70% 105 79 112 81 119 83 126 85 134 87

75% 109 81 116 83 124 85 132 87

80% 113 83 121 85 129 87

85% 117 85 126 87 135 89

90% 122 87 131 89

100 102

HI DP HI DP

10% 95 34 97 35

15% 96 44 98 45 80-90 Degrees -- Caution

20% 97 52 100 53 91-104 Degrees -- Extreme Caution

25% 100 58 103 60 105-125 Degrees -- Danger

30% 102 63 106 65 125+ Degrees -- Extreme Danger

35% 106 68 110 70

40% 109 71 114 73

45% 114 75 119 77

50% 118 78 124 80

55% 124 81 130 83

60% 129 84 137 85

65% 136

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Required amount of H2O (gram) per kg air to reach the desired

relative humidity:

which equals for the space mentioned above:

At an adopted weight of one cubic metre of air of kg/m3, needs to be added to the air withinthe room to achieve the above-mentioned relative humidity.


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Imagine: there is a building in which60

% of the air is recycled and is refreshed by outside air. How

much moist must be added to this air? must be added.

According to this method, one can determine how much moist a moisturizer must spray. In practise, one should adopta worst-case scenario. For example, in winter at an outside temperature of -10 C and a relative humidity of 30%, one

wishes to create a satisfactory indoor climate (such as 20 C and a minimal relative humidity of 40%). There appearsto be a direct relation between relative humidity and phsychological wellfare of humans. Humans feel their best at a

relative humidity of 40% or above.

This data is based on estimates, because relative humidity cannot be measured accurately in outside air. When it israining, relative humidity draws near 100% and when it is a cold day, relative humidity is very low. Principally, whenair is warmer, it can contain more fluids. When air is heated, but not moisturized, relative humidity will decrease,whereas the number of grams of H2O per kilogram remains the same.

Another example: how much water vanishes from a smokestack which emits 80,000 Nm3/hour of water-saturized air(100% RH) that has a temperature of 75 C? (answer = 31,394 litres/hour or a reversed waterfall).

Naturally, this can all be controlled by a Mollier diagram. Example: at a temperature of 20 C, the relative humidity is

measured 50%. One can now appoint the density as 1,20 kg/m3and there will be about 7,3 g of water per kg of air.

What are the correct amounts of relative humidity for a correct environment?

For a pleasant working environment, it is important to make sure relative humidity does not fall below 40%. Whenrelative humidity is less than 40%, the risk of disease is increased. Generally, it can be stated that symptoms that arecaused by dry air vary, but three main factors can be distinguished: static electricity, moisture stability and healtheffects.

Static electricity

Dry air can cause static electricity in an environment. Static electricity can be diminished by increasing the relativehumidity of air. Machines in a machine park give off static electricity as a result of friction. When there are moremachines present that are active during a longer period of time, more friction will take place and the risk of staticelectricity increases. This mainly occurs at dry machine elements. In computer rooms, there is also a static electricityrisk. Most static electricity is caused at a relative humidity of between 30 and 35%.

Moisture stability

Moisture stability means the ability of a material or product to maintain a certain level of moisture, despite fluctuationsof relative humidity in its environment. Most materials give off or take up moist. This can cause damage to a material

or product. In many sectors such as vegetables, fruits, flowers and granes- this process is irreversible. When relativehumidity is too high, this can also cause problems for antiques, paintings, books, papers, etc. Most damage to olderproducts is caused by air humidity fluctuation.

Health effects

As temperatures increase, relative humidity decreases. Dry air can cause health effects, such as dry nose and throat.This causes a higher susceptivity to pathogens such as viruses. When it is cold, a higher air humidity makes peoplebelieve it is warm. This causes the heater to be on less often.

It appears that the climate for bacterial growth is worst when relative humidity is between 40 and 60%. Viruses can

survive least at a relative humidity of between 47 and 70%. For people, relative humidity is most pleasant between 40and 60%. For people that suffer from allergies and astma, relative humidity must be between 45 and 55%.

High relative humidity can cause constriction.

Desirable relative humidity and temperature for each activity

Below, a table is shown that outlines ideal temperatures and relative humidity for each sector in a given situation. Thistable is derived from JDK air-handlin

Read more:http://www.lenntech.com/calculators/humidity/relative-humidity.htm#ixzz2hGuRzagc
http://www.lenntech.com/calculators/humidity/relative-humidity.htm#ixzz2hGuRzagchttp://www.lenntech.com/calculators/humidity/relative-humidity.htm#ixzz2hGuRzagchttp://www.lenntech.com/calculators/humidity/relative-humidity.htm#ixzz2hGuRzagchttp://www.lenntech.com/calculators/humidity/relative-humidity.htm#ixzz2hGuRzagc


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Effects of the heat index (shade values)[edit]

Celsius Fahrenheit Notes

2732 C 8090 FCaution: fatigue is possible with prolonged exposure and activity. Continuing activity could result

inheat cramps.

3241 C 90105 FExtreme caution:heat crampsandheat exhaustionare possible. Continuing activity could result

inheat stroke.

4154 C105130

FDanger:heat crampsandheat exhaustionare likely;heat strokeis probable with continued activity.

over

54 Cover 130 F Extreme danger:heat strokeis imminent.

Exposure to full sunshine can increase heat index values by up to 8 C (14 F).[7]

Formula[edit]

The formula below approximates the heat index in degrees Fahrenheit, to within 1.3 F. It is the result of a multivariate fit

(temperature equal to or greater than 80F and relative humidity equal to or greater than 40%) to a model of the human

body.[8][9]

This equation reproduces the above NOAA National Weather Service table (except the values at 90F & 45%/70%

relative humidity vary unrounded by less than -1/+1, respectively).

where

= heat index (in degrees Fahrenheit)

= ambientdry-bulb temperature(in degrees Fahrenheit)

= relative humidity (percentage value between 0 and 100)

An alternative set of constants for this equation that is within 3 degrees of the NWS master table for

all humidities from 0 to 80% and all temperatures between 70 and 115 F and all heat indexes < 150

F is

A further alternate is this:[10]
http://en.wikipedia.org/w/index.php?title=Heat_index&action=edit&section=4http://en.wikipedia.org/w/index.php?title=Heat_index&action=edit&section=4http://en.wikipedia.org/w/index.php?title=Heat_index&action=edit&section=4http://en.wikipedia.org/wiki/Heat_cramphttp://en.wikipedia.org/wiki/Heat_cramphttp://en.wikipedia.org/wiki/Heat_cramphttp://en.wikipedia.org/wiki/Heat_cramphttp://en.wikipedia.org/wiki/Heat_cramphttp://en.wikipedia.org/wiki/Heat_cramphttp://en.wikipedia.org/wiki/Heat_exhaustionhttp://en.wikipedia.org/wiki/Heat_exhaustionhttp://en.wikipedia.org/wiki/Heat_exhaustionhttp://en.wikipedia.org/wiki/Heat_strokehttp://en.wikipedia.org/wiki/Heat_strokehttp://en.wikipedia.org/wiki/Heat_strokehttp://en.wikipedia.org/wiki/Heat_cramphttp://en.wikipedia.org/wiki/Heat_cramphttp://en.wikipedia.org/wiki/Heat_cramphttp://en.wikipedia.org/wiki/Heat_exhaustionhttp://en.wikipedia.org/wiki/Heat_exhaustionhttp://en.wikipedia.org/wiki/Heat_exhaustionhttp://en.wikipedia.org/wiki/Heat_strokehttp://en.wikipedia.org/wiki/Heat_strokehttp://en.wikipedia.org/wiki/Heat_strokehttp://en.wikipedia.org/wiki/Heat_strokehttp://en.wikipedia.org/wiki/Heat_strokehttp://en.wikipedia.org/wiki/Heat_strokehttp://en.wikipedia.org/wiki/Heat_index#cite_note-Pueblo-7http://en.wikipedia.org/wiki/Heat_index#cite_note-Pueblo-7http://en.wikipedia.org/wiki/Heat_index#cite_note-Pueblo-7http://en.wikipedia.org/w/index.php?title=Heat_index&action=edit&section=5http://en.wikipedia.org/w/index.php?title=Heat_index&action=edit&section=5http://en.wikipedia.org/w/index.php?title=Heat_index&action=edit&section=5http://en.wikipedia.org/wiki/Heat_index#cite_note-8http://en.wikipedia.org/wiki/Heat_index#cite_note-8http://en.wikipedia.org/wiki/Heat_index#cite_note-8http://en.wikipedia.org/wiki/Dry-bulb_temperaturehttp://en.wikipedia.org/wiki/Dry-bulb_temperaturehttp://en.wikipedia.org/wiki/Dry-bulb_temperaturehttp://en.wikipedia.org/wiki/Heat_index#cite_note-10http://en.wikipedia.org/wiki/Heat_index#cite_note-10http://en.wikipedia.org/wiki/Heat_index#cite_note-10http://en.wikipedia.org/wiki/Heat_index#cite_note-10http://en.wikipedia.org/wiki/Dry-bulb_temperaturehttp://en.wikipedia.org/wiki/Heat_index#cite_note-8http://en.wikipedia.org/wiki/Heat_index#cite_note-8http://en.wikipedia.org/w/index.php?title=Heat_index&action=edit&section=5http://en.wikipedia.org/wiki/Heat_index#cite_note-Pueblo-7http://en.wikipedia.org/wiki/Heat_strokehttp://en.wikipedia.org/wiki/Heat_strokehttp://en.wikipedia.org/wiki/Heat_exhaustionhttp://en.wikipedia.org/wiki/Heat_cramphttp://en.wikipedia.org/wiki/Heat_strokehttp://en.wikipedia.org/wiki/Heat_exhaustionhttp://en.wikipedia.org/wiki/Heat_cramphttp://en.wikipedia.org/wiki/Heat_cramphttp://en.wikipedia.org/w/index.php?title=Heat_index&action=edit&section=4


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where

For example, using this last formula, with temperature 90 F (32 C) and relative

humidity (RH) of 85%, the result would be: Heat index for 90 F, RH 85% =114.9.

See also

Introduction.

Relative humidity (RH) is the actual amount of water vapor in the air as a percentage of the maximum amount of water vapor which theair could hold at a given temperature. When air is warmed, its ability to hold water vapor is increased, and when cooled, it can hold lesswater vapor. If the amount of water vapor in the air were held constant as the temperature was increased, this would cause the relativehumidity to fall, because the warm air would now be able to hold more water vapor then when it was cool. In the winter, as cold, moistoutdoor air is brought indoors and heated, it becomes warm, dry air just by being heated. Air at 20oF & 70% RH, when heated to 72oF,will have a relative humidity of just 8%. Humidifiers bring the relative humidity back to the normal levels we need for comfort, safety &protection from drying.

11/2 Ounces of water, 11/2 Ounces ofwater,

Glass only 15% full. Glass is 80% full.

These two glasses representing the same pound of air at different temperaturesare a good visual example of relative humidity. The small glass contains 11/2ounces of water and is 80% full. This could represent a pound of air at 30

oF and

80% relative humidity. If we pour the 11/2 ounces of water from the small glassinto the large glass, we now have only 15% of the glass full. This larger glasswould represent our same pound of air heated to 70oF, but with the same poundof air and the same water vapor content we now have only 15% relativehumidity.


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Application.

For a humidification application we are basically interested only in how much dry air is entering the space to be humidified. If we have aroom in which we wanted to maintain 70

oF and 50% relative humidity, and the room was air tight with a vapor barrier, we would only

have to introduce the proper amount of water into the air once. If we maintain a constant 70oF we would also maintain a constant 50%

RH. This would be due to the fact that no dry air could get in to mix with our conditioned air and no moisture could get out. But, even ourmost modern buildings are not that tight. Outside air enters through open doors, cracks, ventilation, make-up air or exhaust systems.This leakage flow is called infiltration.

Ground Rules for Estimating.

In estimating a humidification application we must find :1. Indoor design condition: The desired temperature and relative humidity. For example, 70oF and 50% RH. The psychrometric chartgives the amount of moisture in the air at these conditions as 55 gr/lb.

2. Outdoor design condition: The given winter temperature and relative humidity for the location. It is the temperature for which heatingsystems are designed. For example, it may be -10oF and 40% RH (moisture = 2gr/lb.) in the North, or 35oF and 60% RH (moisture = 17gr/lb.) in the South.

3. Volume of outside air entering the space to be humidified.

Calculations

In a residence, outside air enters by natural infiltration, which in turn, depends on tightness of construction. Typically this varies from 1/4to 1 air volume exchange per hour and may be more with a f ireplaces or fresh air exchange devices. In a factory, warehouse or otherbuildings without air ducts, infiltration, exhaust fans or loading docks are the major sources of fresh air. Infiltration is difficult to calculateand is usually an engineering estimate based on a percentage of total volume. Example: A building with 100,000 cubic feet of space.There is no mechanical ventilation or make-up air system. Assume 1 air change per hour. The outdoor heating design temperature is0

oF and we require 50% RH at 70

oF. The formula for H (lbs/hr) is:

H = Volume X Air Changes X Grains of Moisture RequiredSpecific Volume X 7000

Grains of Moisture Required From psychrometric chart = 56 grains of moisture per pound of air at 70oF and 50% RH, minus 9 grains ofmoisture per pound already in the air (56 - 9 = 47). Specific Volume From psychrometric chart = 13.5 cu. ft./lb. of air at 70

oF, 50% RH

and 7,000 = Number of grains per pound of water, a conversion constant.

heater air design

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