HVAC: ARE Building Systems

4. HVAC
Fan coil with four pipe system carries two pipes for heating and two pipes for cooling:
Not: Evaporative cooling, domestic hot water circulation, high rise fire safety systems
In a setting where the fan is obligated to have a bend, bend with 45 degrees is far better than 90 degrees or variation thereof.

Constant volume reheat has the highest operating cost for a large office building.
Not: Single zone- constant volume (small office), variable air volume, Double duct-constant volume
Single duct, Variable Air Volume systems are more efficient than constant volume system because: in a VAV system, with variable-pitch blades or variable-speed fans allow air to modulate from zero to maximum
Not: Fan runs at efficient levels and air volumes are controlled by manual dampers, duct sizes are reduced to save initial cost, low voltage equipment are needed
In a house design, the presence of a tree is positioned, depending the am vs pm, the sun moves. In North direction, No sun. In East direction the sun is from east and tree in east will block in morning, and south, the tree shades vary from morning to afternoon and in west, the sun is straight through glazing, therefore the tree can be placed on west.

Cooling tower using the water takes the heat away from building by spraying water over coils and passing air to cool the water
Not: Cooling coil, dehumidifier, heat pump

Chiller/cooling tower steps: Cooling tower to chiller is water: water is pumped from chiller to cooling tower for heat removal, the Freon and chiller are getting cool by cooling tower water in a heat exchanger, finally water is pumped into room and removes heat from room in fan coils.

U value of wall assembly: includes Resistance of air, wall, studs, interior and exterior film
Not: Orientation
Source of a building’s heat loss: Air infiltration
Not: Occupants, isolation, electric lightning
Psychometric chart plot factors: Relative humidity, air temperature
Not: Air motion, mean radiant temperature, convection current, surface temperature
Equation for U * area *temperature difference= heat gain: Often underestimates summer heat gain since roof color (cool roof), roof mass and time of day also affects the heat gain.
Not: Entropy, roof texture, relative humidity
Heat is described through: Convection, conduction, radiation, enthalpy