Question
The air conditioning by evaporative cooling in Problem 11.101 is modified by adding a dehumidification process before the water spray cooling process. This dehumidification is achieved, as shown in Fig. $\mathrm{P} 11.144,$ by using a desiccant material, which absorbs water on one side of a rotating drum heat exchanger. The desiccant is regenerated by heating on the other side of the drum to drive the water out. The pressure is $100 \mathrm{kPa}$ everywhere, and other properties are indicated on the diagram. Calculate the relative humidity of the cool air supplied to the room at state 4 and the heat transfer per unit mass of air that needs to be supplied to the heater unit.
Step 1
From the problem, we know that \(h_B5 = -316 \, \text{kJ/kg}\) and \(h_F6 = 630 \, \text{kJ/kg}\). Substituting these values into the formula, we get: \[w_5 = -316 \, \text{kJ/kg} - 630 \, \text{kJ/kg} = -946 \, \text{kJ/kg}\] Show more…
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An air-conditioning system operates at a total pressure of 1 atm and consists of a heating section and an evaporative cooler. Air enters the heating section at $15^{\circ} \mathrm{C}$ and 55 percent relative humidity at a rate of $30 \mathrm{m}^{3} / \mathrm{min},$ and it leaves the evaporative cooler at $25^{\circ} \mathrm{C}$ and 45 percent relatively humidity. Determine ( $a$ ) the temperature and relative humidity of the air when it leaves the heating section, $(b)$ the rate of heat transfer in the heating section, and $(c)$ the rate of water added to air in the evaporative cooler.
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One means of conditioning hot summer air is evaporative cooling, which is a process similar to the adiabatic saturation process. Consider outdoor ambient air at $35^{\circ} \mathrm{C}, 100 \mathrm{kPa}, 30 \%$ relative humidity. Find the lowest temperature this can generate and mention some disadvantage with this technique. Solve the problem with the energy equation and formulas and repeat it using the psychrometric chart, Fig. E.4.
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