ceiling air conditioner

Like a refrigerator or air conditioner, these systems use a heat pump to force the transfer of heat. Heat pumps can transfer heat from a cool space to a warm space, against the natural direction of flow, or they can enhance the natural flow of heat from a warm area to a cool one. The core of the heat pump is a loop of refrigerant pumped through a vapor-compression refrigeration cycle that moves heat. Heat pumps are always more efficient at heating than pure electric heaters, even when extracting heat from cold winter air.

But unlike an air source heat pump , which transfers heat to or from the outside air, a water source heat pump exchanges heat with the ground. This is much more energy-efficient because underground temperatures are more stable than air temperatures through the year. Seasonal variations drop off with depth and disappear below seven meters due to thermal inertia.

Like a cave, the shallow ground temperature is warmer than the air above during the winter and cooler than the air in the summer. A water source heat pump extracts ground heat in the winter (for heating) and transfers heat back into the ground in the summer (for cooling). Some systems are designed to operate in one mode only, heating or cooling, depending on climate.

The setup costs are higher than for conventional systems, but the difference is usually returned in energy savings in 3 to 10 years. System life is estimated at 25 years for inside components and 50+ years for the ground loop.As of 2004, there are over a million units installed worldwide providing 12 GW of thermal capacity, with an annual growth rate of 10%. If deployed on a large scale, this technology may help reduce energy costs and alleviate global warming.

from:http://zhonglv.blogtownhall.com/

Ducts are used in heating, ventilation, and air conditioning (HVAC) to deliver and remove air. These needed airflows include, for example, supply air, return air, and exhaust air.Ducts also deliver, most commonly as part of the supply air, ventilation air. As such, duct air conditioner are one method of ensuring acceptable indoor air quality as well as thermal comfort.

A duct system is often called ductwork. Planning ('laying out'), sizing, optimizing, detailing, and finding the pressure losses through a duct system is called duct design.

The position of the U.S. Environmental Protection Agency (EPA) is that "If no one in your household suffers from allergies or unexplained symptoms or illnesses and if, after a visual inspection of the inside of the ducts, you see no indication that your air ducts are contaminated with large deposits of dust or mold (no musty odor or visible mold growth), having your air ducts cleaned is probably unnecessary."

Studies by the EPA and the Canadian Mortgage and Housing Corporation (CMHC) in the 1990s has lead CMHC to conclude that "duct cleaning will not usually change the quality of the air you breathe, nor will it significantly affect airflows or heating costs".

from:http://zhonglv.blogtownhall.com/