Quiz 4 - MENG 3211 SP2020 PDF

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MENG 3211 –Thermal Fluids lab

Quiz 4 – Psychometrics Name: ________ A new HVAC system is been tested at the laboratory. The experimental data for the humid air at the inlet and outlet are:

Inlet conditions:

Outlet conditions:

Dry bulb temperature: 33.4 °C

Dry bulb temperature: 22.0°C.

Relative humidity: 40%

Dew point temperature: 18.0°C

The mass flow rate of dry air is 100 kg/s. Assume that the temperature of the condensate water is equal to the dew point of the outlet air at the evaporator and assume that conditions are under standard atmospheric pressure.

1. Determine the mass rate of removed in HVAC system in kg/s. m ´ = 0.0129 * 100 = 1.29 kg/s

2. Determine the total sensible heat in kW. hs

= C p , air

m ´ air

ΔT

= 1.006 * 100 * (33.4-22) = 1147kW 3. Determine the total latent heat in kW.

hl =

∆ H vap m ´ air ∆ ω

= 2454 * 100 * (0.012935638 – 0.012904318) = 7.69kW

MENG 3211 –Thermal Fluids lab

4. Calculate the total amount of heat transferred in kW. ht

= hl +

hs

= 7.69 + 1147 = 1154.69kW For different given conditions, Initial condition: relative humidity (RH) 70% and dry-bulb temperature (Tdb) 33.0 °C. Final condition: relative humidity (RH) 30% and dry-bulb temperature (Tdb) 24.0 °C.

5. what is the change in water content (in gw/kgda)?

∆ w=¿ (0.0055 – 0.0224) * 1000 = -16.9

gw kgda

6. was water added or removed? Since change in water content resulted in a negative number it means that water was removed

MENG 3211 –Thermal Fluids lab

Methodology The experimental apparatus includes two types of hygrometer; a Bacharah sling hygrometer and capacitive humidity sensor thermo-hygrometer. The psychrometer consists of two glass thermometers which measures both dry air temperature and wet-bulb temperature. Apparatus Table 1: List of the equipment used during the experiment with their respective uncertainty

Equipment Bacharach sling hygrometer Omega Digital psychrometer

Uncertainty ± 5%1 ± 3%

RH92 1: Bacharach

Setup

Figure 1: Drawing of sling psychrometer

Experimental Procedure 1. Dip and soak the cloth of the sling psychrometer in water. 2. Carefully start swinging the sling psychrometer around. 3. Using the digital psychrometer determine the dry bulb temperature , wet bulb temperature and relative humidity. 4. Repeat steps 1-3 with other group members 5. Using the psychrometric chart determine the specific humidity, enthalpy, dew point, latent heat and sensible heat. 6. Using that above gained information answer the following questions. Is the indoor air humidified or dehumidified compared to outdoor air? Is the indoor air warmer or colder compared to outdoor air? 7. Estimate the uncertainty of error associated with each measurement taken.

MENG 3211 –Thermal Fluids lab...