Thermal Balance and Psychrometric Analysis in Air Conditioning

Posted on May 4, 2024 in Physics

THERMAL BALANCE

PROFIT OUTSIDE:

Sensible-Heat Transfer
Qt = K (coefficient of thermal transmittance) x Area x (te – ti) Kcal / h = (kcal/h.m2. º C) x m2 x º C

Heat Radiation-Sensitive
Qr = K x sup x R (value arising from the incidence table of the sun according to the season, the cladding materials and latitude of the building) Kcal / h = (kcal/h.m2. º C) x m2 x º C

INTERNAL INCOME:

People-Heat-Sensitive Latent Heat +
Qps = No. of persons x Kcal / h (sensible) table per person depending on activity.
Qpl = No. of persons x Kcal / h (latent) of tablapor person depending on activity.

Heat-Sensitive Iluminción
Qi = No. Watt (20 to 30watts x m2) x 0.86Kcal / h = Kcal / h Watt

Heat-Sensitive Equipment
Qe s = D teams (Sum of power of all teams) x 0.86 kcal / h.watt.

VENTILATION.

Outside air. LATENT HEAT HEAT SENSITIVE +
Qs = Ce (0.24Kcal/Kg º C) x V (volume of air arises from activity table according m3) x Pg (1.14 specific gravity air Kg/m3) x (te – ti)
Ql = L (latent heat of steam 0.576Kcal/gr) x V (volume of air activity table according m3 x) x Pg (1.14 specific gravity air Kg/m3) x (Me – Mi) (specific humidity of air 4 , 3gr/kg)

Total Heat Gain: The gain by the addition of outside air + (Total Winnings Sensible Heat + 10%) + (Total Winnings Latent Heat + 5%)

Psychrometric
(He studies the properties of moist air)

Relationship between variables: With increasing temperature, pressure and humidity decreases

Data:
Internal Relative Humidity and Indoor Temperature (making the point I)
Relative Humidity and Temperature Exterior Exterior (According to item E)

Concepts:

Heat: Demonstration of energy caused by motion of the molecules of a body

Specific Heat (EC Kcal / Kg ° C): amount of heat needed to make 1 kg. Of a substance increases its temperature by one degree centigrade. The specific heat varies with temperature and gases in terms of pressure. Its unit is Kcal / kg º C.

Calorie (Kcal): The amount of heat required to raise a 1 degree Celsius degree centigrade temperature of one kilogram of distilled water at atmospheric pressure.

Sensible heat (Qs Kcal / hr): Heat that is manifested through a change in temperature of a substance and is measured with a thermometer. The temperature may increase or decrease.

Latent Heat (Ol kcal / hour): Heat supplied to or subtracted from a substance causes a change in state without changing the temperature.

Total heat (Qt Kcal / hr): Sum of sensible heat and latent heat.

Dry Bulb Temperature (TBS º C): Temperature can be read with an ordinary thermometer. In abacus you read on the horizontal axis.

Wet bulb temperature (TBH º C): Product temperature is measured with an ordinary thermometer with the bulb covered with a wet cotton cloth.

Dew Point Temperature (T º C). Temperature at which water vapor in moist air condenses and begins to separate.

Specific Humidity (SH g / kg) Amount of water in grams which contains moist air per kilogram of dry air)

Relative Humidity (RH%): HR = HEspecífica air húmdedo / HE saturated air

Enthalpy (E Cal / kg): heat content of moist air. E = Qsensible air + fluid + Qsensible water evaporated Qlatente

Sensible Heat Factor (FCS): FCS = Qsensible / (Qsensible + Q latent)

Specific volume (VE m3/kg): Reverse the specific weight of dry air

Processes that are read from the psychrometric abacus

  1. Cooling.
  2. Warming.
  3. Humidification
  4. Dehumidification
  5. Cooling Humidification.
  6. Cooling and Dehumidification.
  7. Warming and humidifying.
  8. Heating and Dehumidification.

Cycle Air Conditioning Refrigeration process

  1. Changing the temperature.
  2. Changing the relative humidity.
  3. Circular and renew the air.
  4. Distribute the air giving the feeling of well being by regulating speed on the exit of the teams.

Using the Psychrometric Abacus

  1. Determining the FCS: FCS = Qsensible / (latent Qsensible + Q) (The mark on the abacus)
  2. Determining the conditions of RH and temperature inside the Home (detail) (making the point I):
    Temperature: 25 ° C
    HR: 50%
  3. Identifying the conditions of RH and temperature outside the Home (detail) (making the point E):
    Temperature: 35 º C
    HR: 40%
  4. are joined in abacus points I and E (He shows the variations that will suffer in the abacus in the cooling process)
  5. Trace of the FCS line with the point P (point already defined in the table)
  6. Determination of the point C (Drawing the line parallel P-FCS that part of section I and intersects with the curve of 95% RH)
  7. The point C indicates the limit to which air can cool the treaty, which reveals the following data:
    TBS at point C
    HR at point C
    VE at point C
    Heat (E) in Section C
  8. Calculation of Weight of Air: W (Kg / hr) = Qsensible (Kcal / h) / CE (0.24Kcal/kg º C) x (TBS and C – C TBH)
  9. Calculation of Air Flow Control (MAC m3/hr): CAM (m3/hr) = W (Kg / hr) x VE (cm3 / g) in C
  10. Calculation of Outdoor Air Flow (m3/hr CAE): CAE (m3/hr) = No. of persons x Renewals Time (m3/hr)
    CAE least equal to or greater than 20% of CAM

Renewals destination local time according to condition:
Housing / Hotels / Offices: 17 to 25m3/hora
Cinemas / Theaters (where there are smokers): 8 to 12m3/hora
Conference Rooms / Restaurants crowded: 35 to 50m3/hora

  1. Calculation of recirculated air flow: CAR (m3/hr) = CAM – CAE
  2. Determination of the point M (Given the IE line representing 100% of treated air, to score in the same line for 20% or more for the CAE and 80% or less for the CAR. At the meeting point between the two segments defined point M, which reveals the following data:
    TBS at point M
    Enthalpy (E) at point M
  3. Calculation of heat to remove the Equipment (Kcal / hour):
    R (Kcal / h) = W (weight of air kg / hr) x (Enthalpy at point M Kcal / kg – at C Enthalpy kcal / kg)
  4. Calculation of the cooling load requirement: R (Kcal / hr) / 3024Kcal/hora