Heating systems

     - early on most dwellings used a fire in each room of a house or building, but as buildings became more complex
     this became a problem
     - central heating systems generate heat from one location and transfer it to various locations in the building

Hot water systems

     - a fuel is burned to heat up water in a central area and the hot water is transferred throughout the building
     - usually a pump of some type keeps the materials flowing throughout the system
     - the rooms themselves are heated by convection currents off of the baseboard heaters

Steam Heating

     - are the same as hot water except steam is produced and it is steam that is transferred throughout the building
     - when the steam gives off its heat it changes back to liquid and flows back to the heating chamber

Radiant Hot water

     - as in the above systems water is heated and transferred to the rooms
     - in this case the tubing is underfoot and releases its heat more evenly in the room

Radiant electric

     - electricity passes through wires or coils in the floor, ceiling walls etc and like a toaster they heat up and release
     heat into the room

Warm air

     - fuel is burned in a furnace and the hot air is forced through ducts throughout the house
     - the rooms are heated by convection currents and controlled with a thermostat

Heat Pumps

     - these systems are relatively new and require new technology
     - they work on the principle that all things contain heat even cold things and that heat can be brought in from one
     place and used somewhere else
     - the key is the heating coil which contains a liquid that evaporates at very low temperatures ( usually outside in the
     ground or pond)
     - this evaporated gas is then compressed which increases its temperature (Boyles Law) and can be used to heat a
     home
     - later it is decompressed and returned to pick up heat from outside the home

Solar heating

     - active solar systems require devices to collect the suns heat (solar panel collector) and then circulate it around
     the home or to a storage tank for later use
     - passive solar heating allows a home to be heated and cooled according to its position relative to the sun so home
     design is critical if it is to be effective

          - in winter you want sun in to heat up the house
          - in summer you want shade to keep the house cool

Insulation

     - material that does not allow heat to be transferred is called an insulator
     - heat can be transferred in three ways so insulating material needs to take into account all three heat loss
     pathways

          - conduction, needs contact so putting spaces between objects is used
          - convection, needs free moving air so break up air pockets or make pockets vacuums by removing
          air
          - radiation, can be turned around by shiny surfaces

     - a well insulated home will cost less to heat and to cool by keeping the heat in in the winter and out during the
     summer

Cooling systems

     - the process of evaporation removes heat from one place in order to evaporate the liquid at another
     - all cooling systems (freezers, fridges etc.) have 4 parts: storage tank, compressor, freezer, condenser coils
     - it works in a similar way as a heat pump in that a liquid ( refrigerant) that evaporates easily (freon) is used to
     collect heat from inside the fridge
     - it is compressed which increases it s temperature and then sent to the condenser coils which cause it to cool and
     release its heat to the outside, changing it back to a liquid

Heat engines

     - convert heat energy into mechanical energy ( movement) in order to do work

External combustion engines (steam engines)

     - the burning of the fuel is outside the chamber with the piston
     - water is heated to make steam which is then directed to another location to move a piston back and forth inside
     a cylinder
     - modern steam engines push turbines instead of pistons

Internal combustion engine (car engines)

     - the burning of the fuel (combustion) occurs directly inside the cylinder or engine
     - the steps or strokes in an engine are used to classify the type of engine
     - in a 4 stroke engine the following occur

          - intake- as piston moves down it sucks in fresh fuel
          - compression- the piston drives up and compresses the air fuel mixture
          - power- the mixture is ignited by a spark causing an explosion driving the piston down
          - exhaust - the remains of the ignition are pushed out of the cylinder getting it ready for the next
          stroke
          - in diesel engines there is no spark, the compression of the mixture is enough to cause the explosion

Thermal pollution

- much of the heat made by industry is not used and must be released
- if it is released into a river then the river will become hotter and the amount of oxygen it can hold will go down affecting the
living things in the water
- to avoid this many industries use cooling ponds or cooling towers to bring the temperature of the waste water down before
releasing it into the rivers or streams