Mechanical Ventilation System - Report Example

Ventilation, electrical heating and domestic fridge Ventilation Without a mechanical ventilation system, the amount of fresh air that enters a home is largely a matter of chance. "Natural ventilation" – the kind you get by opening windows – just doesnt do the best job, because it tends to provide either too much or too little ventilation. The only way to ensure adequate ventilation is to install some type of automatically controlled ventilation system. As youll see, you have quite a few choices. Ventilation serves three important functions: * Expel stale air containing water vapor, carbon dioxide, airborne chemicals and other pollutants. * Draw in outside air, which presumably contains fewer pollutants and less water vapor. * Distribute the outside air throughout the house. * Control system operation automatically. The equipment that performs these four basic functions comes in all shapes, size and costs. Here are some sample systems: Surface-mounted Fan The simplest controlled ventilation system uses a quiet, high-quality surface-mounted fan. Fresh air enters through passive vents located in window sashes or outside walls. Surface-mounted fans provide good ventilation for smaller areas. Large houses may need more than one. Remote-mounted In-line Fan Remote-mounted fans can pick up stale air from a single point. Or, they can be attached to a branched duct system with picks ups in two or three locations. This makes them a good choice for large houses. If properly rated, the fan could be attached to a range hood. Remote-mounted Multiport Fan. Large houses and several multifamily units can be ventilated by a single multiport fan. Some units can accept a duct from the range hood. Most operate at two or more speeds. Several manufacturers sell complete kits with all the ducts and accessories. These may cost a bit more, but the kits simplify installation. Balanced Ventilator If you want balanced operation, without the extra expense of heat recovery, these would be a good choice. Only one or two manufacturers make balanced ventilators without heat recovery. Air-to-Air Heat Exchanger This type of heat-recovery ventilator provides balanced air flow and recovers up to 85 percent of the heat from outgoing air. By warming the incoming air, AAHXs provide greater comfort in cold climates than other types of ventilation systems. Units can be sized for any home and small commercial buildings. Exhaust Air Heat Pump By employing a heat pump unit about the size of a window air conditioner, an exhaust air heat pump (EAHP) offers exceptional heat recovery efficiency. It can also provide most of the hot water needed by an average family. While the exhaust fan is controlled by timers, heat recovery engages only when hot water is needed. Some other forms are: * Bathroom Exhaust Fans Bathroom fans not only exhaust offensive odors, they pipe vast amounts of humid air to the exterior of your home. * Ceiling Fans Ceiling fans can keep you cool and save lots of money. The best ceiling fans have balanced motors and blades. * Dryer Vent Dryer vents need to be cleaned on a regular basis. The flapper door on exterior dryer-vent housings must be checked for lint buildup. * Whole House Fans and Attic Fans Solar attic fans are a new group of products that use solar energy to move hot attic air. Attic exhaust fans remove hot air from attic spaces, while whole house fans remove hot air from both living spaces and the attic at the same time. * Whole House Fan in Cathedral Ceiling Whole house fans provide enormous air movement through out your home. Install one in a home with a cathedral ceiling. It can be done. * Crawl Space Vents Crawl spaces collect and condense water vapor. Crawl space ventilation is necessary to prevent mildew or rot. Vapor barriers may provide better protection than crawlspace vents. * Roof Ventilation with Turbine Vents Turbine vents can replace the hot air in your attic in minutes. Mother Nature blows across the fins in the roof turbine vents as they exhaust the heat build up. Electric heater An electric heater is an electrical appliance that converts electrical energy into heat. The heating element inside every electric heater is simply an electrical resistor, and works on the principle of Joule heating: an electric current flowing through a resistor converts electrical energy into heat energy. Although they all use the same physical principle to generate heat, electric heaters differ in the way they deliver that heat to the environment. Several types are described in the sections below. Radiative heaters or "space heaters" Radiative heaters contain a heating element that reaches a high temperature. The element is usually packaged inside a glass envelope resembling a light bulb and with a reflector to direct the energy output away from the body of the heater. The element emits infrared radiation that travels through air or space until it hits an absorbing surface, where it is partially converted to heat and partially reflected. This heat directly warms people and objects in the room, rather than warming the air. This style of heater is most useful in an area that is unable to be kept with minimal airflow. They are also ideal for basements and garages since they are good at spot heating. They are an excellent choice for task specific heating. Convection heaters In a convection heater, the heating element heats the air next to it by conduction. Hot air is less dense than cool air, so it rises due to buoyancy, allowing more cool air to flow in to take its place. This sets up a constant current of hot air that leaves the appliance through vent holes and heats up the surrounding space. They are ideally suited for heating a closed space. They operate silently and have the lowest risk of ignition hazard in the event that they make unintended contact with furnishings. This is a good choice for long periods of time or if left unattended. They are very safe heaters and there is a very low chance of getting burned. Fan heaters or "forced convection heaters" A fan heater is a variety of convection heater that includes an electric fan to speed up the airflow. This reduces the thermal resistance between the heating element and the surroundings, allowing heat to be transferred more quickly. Storage heating A storage heating system takes advantage of cheaper electricity prices, sold during low demand periods such as overnight. In the United Kingdom, this is branded as Economy 7. The storage heater stores heat in clay bricks, then releases it during the day when required. Domestic electrical underfloor heating These systems are called radiant heating systems, regardless of whether they include a heat exchanger (also called a radiator) or are electrically powered. When a home radiant heat system is turned on, current flows through a conductive heating material. The heated material then heats the flooring until it reaches the right temperature set by the floor thermostat. The flooring then heats the adjacent air, which circulates, heating other objects in the room by convection. As it rises, the heated air will heat the room and all its contents up to the ceiling. This form of heating gives the most consistent room temperature from floor to ceiling compared to any other heating system. Refrigerator Heat is removed from food and the surrounding area, thereby creating an environment which retards the activity of microorganisms. Temperature is usually about 5°C. A refrigerant is used to remove the heat, i.e., a highly sensitive liquid which converts easily into a gas and back again into a liquid, e.g., freon12 or ammonia. The refrigerant is carried in tubes at the back of the appliance and around the icebox. The electric motor activates the compressor in the appliance which forces a gaseous refrigerant in the compressor into the condenser. In the condenser the refrigerant changes into a liquid, heat from the food in the refrigerator is absorbed by the liquid refrigerant and converts it back into a gas, ready for the cycle to begin again. In so doing, the food is cooled. Block diagram of refrigerator. An absorption refrigerator uses a refrigerant (such as ammonia) and an absorbent (such as water). The cycle consists of four parts: 1. The use of solar heat to drive off the refrigerant as a vapor from the liquid absorbent at the collector temperature. 2. The condensation of the refrigerant, and the rejection of the heat of condensation at ambient temperature. 3. The evaporation of the refrigerant at the refrigeration temperature with the extraction of heat from the refrigeration load. 4. The reabsorption of the refrigerant, and the rejection of the heat of adsorption at ambient temperature. Construction of a refrigerator The outer case is made of enameled steel and the lining is made of plastic, with layers of insulation between them. The door is magnetically sealed. The star marking rating is on the icebox and this refers to the temperature in the icebox and the length of time pre-frozen food can be stored in it. * -6°C Food stored for one week ** -12°C Food stored for one month *** -18°C Food stored for three months **** -24°C Fresh food can be frozen at this temperature Care and cleaning needed. * Do not open the door too often or put hot food in the refrigerator * Do not over pack or leave food uncovered * Defrost regularly if no automatic defrost function exists * Wash inside with warm water and a little bread soda * Wash outside with hot soapy water, rinse and dry with dry cloth (a little furniture polish can be used on the outside). Read More