Heat Pump TEAM A: CAROLINE NAKANWAGI SUNGHEE MIN THERMODYNAMIC 2014 FALL

Overview  What is heat pump? :Thermodynamic principle  How does a heat pump work?  Advantages of heat pump  Energy types used in heat pump :Geothermal energy  Types of heat pump

THERMODYNAMIC PRINCIPLE  Use a volatile evaporating condensing fluid known as the refrigerant  Works by compressing the volatile liquid to make it hotter on the side to be warmed →the release of pressure to the side where heat isn’t being absorbed  The below diagram shows an example of a heat pump 1) condenser, 2) expansion valve, 3) evaporator, 4) compressor.

How a Heat a Pump Works The refrigerant when it’s in the gaseous state, it’s pressurized and then let to flow around the system by a compressor →This makes the vapor extremely hot and it’s cooled in the heat exchanger also known as the condenser →The refrigerant that has been condensed then passes through a metering device →This leads to a reduction in the pressure of the refrigerant →The low pressure refrigerant enters another heat exchanger →Here it absorbs heat and boils →The refrigerant then returns to the compressor and the cycle is repeated

 Generally the heat pump continuously cycles through the processes of Compression →Condensation → Expansion → Evaporation  The heat pump takes heat from the environment and channels it into a space or system which requires heating.

COMPRESSION, CONDENSATION,EXPANSION AND EVAPORATION  Inside the chambers of the heat pump is allowed to expand in a continuous process :when the gas travels through the expansion valve, the gas absorbs heat in the form of stored energy from the air, water or the ground  As the cycle continues, the gas is compressed and it releases the energy in the form of heat  The performance of heat pump is measured by the C.O.P.( Coefficient of Performance) :the ratio of the heat pumped into the hot reservoir to the work input to the heat pump  Heat Pumps aren’t 100% efficient 1 st Therm. Law: energy can be changed from one form to another but can’t be created or destroyed 2nd Therm. Law: work can be converted to heat but the process isn’t 100% efficient

 If the heat pump is doing reversible work, then the Carnot cycle is traversed in the opposite direction  The signs of w and q in the individual segments and the signs of w and q in the overall process are changed  Heat is now withdrawn from the cold reservoir that is the surroundings and deposited into the home, which is the hot reservoir  Since this process isn’t spontaneous, work must be done on the system to effect this direction of heat flow  Heat pumps become less effective as the temperature of the cold air decreases.  Therefore, geothermal heat pumps are better

 Advantages of Heat Pumps Saving energy and money Protecting environment No need of any maintenance  Environmental energy can be from Ambient Air Water Brine (Ground heat)

 What is Geothermal Energy? Geo (Greek for Earth) Thermal (heat) Temperature of Shallow Crust from F(Upper 10 ft.) to 14,400 (Molten Core meter to center of core)

 Brief History of Geothermal Energy Paleo0Indians Usage Dates 10,000 years ago Use by Romans- Hot Spas; Hot Running Water Early 1800s – Yellowstone hot Spring and Hot Spring Arkansas st Commercial Use; Asa Thompson

 Geothermal Potentials Seasonal variations measurable until depth At 10 meters depth the ground is approximately 1K warmer than the yearly than the yearly average ambient temperature In high depth the temperature rises 2.5-4K each 100meter For passive cooling depths of meters are suitable bath in Wooden Tub for $1

 Brine Source Heat Pump  Air Source Heat Pump  Water Source Heat Pump

A. Brine Source Heat Pump : ground heat as the heat source Horizontal Collector Vertical Collector

B. Air Source Heat Pump: air as the heat source-air /water heat pump External Installation Internal Installation

Air Flow in Heat pump

A sectional drawing

C. Water Source Heat Pump: ground water as the heat source–water/water heat pump