Equipment And Components Flashcards
What is the basic premise of a cooling tower and what are the common types?
Cooling towers use the principles of evaporative cooling to reduce the temperature of water. As relatively dry air flows against water, some of the water evaporates and the energy used to do this reduces the temperature of the remaining liquid. The two main types are mechanical flow and natural flow and can be in a cross flow or counter flow configuration.
What is cooling tower range?
What is cooling tower approach?
What is cooling tower effectiveness?
Range: Difference of temperature between the water going in and the water going out.
Approach: Difference between the temperature of the water going out and the wet bulb temperature of the incoming air.
Effectiveness = range / (range + approach)
What pressures are considered low, medium and high in a steam system?
Low: below 15 psi
Medium: between 15 and 150 psi
High: above 150 psi
What is the equation for efficiency of a steam boiler?
Efficiency = (mass flow rate of feed water * (enthalpy steam out - enthalpy feed water in) / (mass flow rate of fuel * high heating value)
What is the total heat equation for a steam boiler?
Q [Btuh] = mass flow rate of fuel * heat value * efficiency
What is the total heat equation for a heat exchanger?
Q = heat transfer coefficient [Btu / (h * ft^2 * F)] * area of heat exchange [ft^2] * LMTD
What is the equation for net refrigeration effect?
Net refrigeration effect [btuh] = mass flow rate [lbs/hr] * (enthalpy entering evaporator [btu/lb] - enthalpy leaving evaporator [btu/lb] )
What is the equation for mechanical horsepower for a pump?
M = (GPM * H [ft. hd.] * SG) / 3956
What is the equation for coefficient of performance for a refrigeration cycle?
COP = net refrigeration effect [Btu] \ (electrical input [Watts] * 3.412 [btu/W])
What is higher heat value and lower heat value?
Higher heat value: heat released in combustion of fuel and condense water from combustion product back down to original combustion temperature. This value is used for condensing boilers.
Lower heat value: heat released in fuel combustion. Used for non condensing boilers
What is the equation for net positive suction head?
NPSHa= suction pressure (gauge) + atmospheric pressure + velocity pressure (V^2 / 2 * g) - vapor pressure of fluid
What is the equation for change in pipe length due to temperature change?
L = original length [in] * thermal expansion coefficient [in / (in * F)] * temperature differential [F]
What are the sensible and total effectiveness equations for an ERV?
Sensible: Q actual / Q max
( OA [CFM] * (OA DB entering - OA DB leaving)) / (OA min * (OA DB entering - EA DB entering))
Total: Q total actual / Q total max
(OA [CFM] * (OA enthalpy entering - OA enthalpy leaving)) / (OA [CFM] * (OA enthalpy entering - EA enthalpy entering))
What are the equations for motor efficiency?
Efficiency = brake HP / motor efficiency = mechanical HP / (motor efficiency * mechanical efficiency)
What are the equations for mechanical HP for a fan?
Fan HP = CFM * TP [ in. wg] / 6356
What are the different MERV ratings and the significant differences?
MERV 6: 35-50% efficient @ 3-10 microns min .6 wg pressure drop
MERV 8: 70-85% efficient @ 3-10 microns. Min .6” wg pressure drop
MERV 11: above 85% efficient @ 3-10 microns, 65-80% efficient @ 1-3 microns. Min 1” wg pressure drop.
MERV 13: above 85% efficient @ 3-10 microns, above 90% efficient @ 1-3 microns, below 75% efficient at .3-1 microns. Min 1.4” wg pressure drop.
