Week 4: Utilities
(Involves)Refrigeration cycle, using the same refrigerant to save cost ✅
Principles
Liquids absorb heat when changed from liquid to gas
Gases give off heat when changed from gas to liquid
Components
Condenser: transfers heat from the refrigerant (e.g. the part behind the fridge that feels hot).
Expansion valve/ throttling device: controls the flow of refrigerant in the refrigerator.
Compressor: raises pressure and temperature of the refrigerant
Evaporator: allows the refrigerant to turn from liquid into gas in the refrigerator, thereby absorbing heat from the contents of the refrigerator.
(refrigerant)enters the inlet and screen as a high-pressure liquid.
(refrigerant flow) restricted by a metered orifice through which it must pass.
(Involves) Electricity: flow of electric charge.
Charges can only move in certain materials; the movement of charges is known as current, I
The SI unit for current is ampere, A
SI unit for electric charge is coulomb (C)
A = C/s
Some concepts ✅
Charges: quantity of electrons in the case of metal conductors, move in a wire/ conductor.
(Water moves through pipe )
Voltage moves the charges (Water pressures moves the water )
Electrical non-conductor – a material that does not allow charges to move.
Electricity flow is impeded by resistance.(Fluid flow is impeded by viscosity )
Electrical conductor – a material that allows charges (electricity) to move.
electrical energy (E) ✅
Electric shock: when a person comes into contact with an electrical energy source
. Electrical energy flows through a portion of the body causing a shock
effects
result in no injury at all or may result in devastating damage or death
Preventions
Avoid water (It increases the conductivity of the electric current.) at all times when working with electricity
Plug a 3-prong extension cord into a grounded outlet
Ohm's Law ✅
Voltage (V) = Current (I) x Resistance (R in ohms)
Power: rate at which energy is transferred.
The unit of power is the watt which is 1 Joule per second
Power = voltage x Current
Refrigerant
Chemical refrigerants are assigned an R number which is determined systematically according to molecular structure.
R-134a: hydro-fluorocarbon (HFC) that does not contribute to ozone depletion; also the first non-ozone-depleting fluorocarbon refrigerant to be commercialized.
widely used in many air conditioning and refrigeration systems globally.
1 electron = 1.6 x 10^-19
Burns are the most common injury from electric shock.
E=Pt, t is in seconds