Ambient air at 1 atm 32 degree C and 60 relative humidity e

Ambient air at 1 atm, 32 degree C and 60 % relative humidity enters a 400 mm internal diameter air-cooling duct with a velocity of 120 m/min. Inside the duct there is a cooling coil. The air leaves the duct saturated at 20 degree C and 1 atm. You also know that the cooling coil is receiving cold water from the local chilled water plant and the temperature of the chilled water when it leaves the cooling coil increases by 6 *C with respect to its inlet temperature. Without using a psychrometric chart determine the amount of water that needs to be supplied to the cooling coil to produce the given exit conditions for the air. Your solution must include hand-calculations and show all the steps required to get the answer. If you need a value for the specific heat of water for the water going inside the cooling coil use 4.16 kJ/kg-K. You are interested in analyzing how changes in the inlet relative humidity of air affect both the required mass flow rate of chilled water needed for the cooling coil and the heat removed from the air. All of the other operating conditions remain unchanged. For your analysis consider the relative humidity of air at the inlet varying from 50% to 90%. Use EES or any other suitable software to study the effect of varying the relative humidity of ambient air that enters the duct. The result of your analysis should be a table that shows the heat removed in kJ/s and chilled water mass flow rate in kg/s ranging from relative humidity 50% to 90% in 5% increments and a plots for heat removed and mass flow rate as a function of relative humidity.

Solution

Standard conditions for temperature and pressure are standard sets of conditions for experimental measurements to be established to allow comparisons to be made between different sets of data. The most used standards are those of the International Union of Pure and Applied Chemistry (IUPAC) and the National Institute of Standards and Technology (NIST), although these are not universally accepted standards. Other organizations have established a variety of alternative definitions for their standard reference conditions.

In chemistry, IUPAC has established two standards:^[1]

The STP and the SATP should not be confused with the standard state commonly used in thermodynamic evaluations of the Gibbs energy of a reaction.

NIST uses a temperature of 20 °C (293.15 K, 68 °F) and an absolute pressure of 1 atm (14.696 psi, 101.325 kPa). This standard is also called normal temperature and pressure (abbreviated as NTP).

The International Standard Metric Conditions for natural gas and similar fluids are 288.15 K (15.00 °C; 59.00 °F) and 101.325 kPa.^[2]

In industry and commerce, standard conditions for temperature and pressure are often necessary to define the standard reference conditions to express the volumes of gases and liquids and related quantities such as the rate of volumetric flow (the volumes of gases vary significantly with temperature and pressure). However, many technical publications (books, journals, advertisements for equipment and machinery) simply state \"standard conditions\" without specifying them, often leading to confusion and errors. Good practice always incorporates the reference conditions of temperature and pressure.