Energy efficiency various types of mechanical systems

Question 1

Mechanical system energy efficiency.

Answer 1

usually based on the ratio of energy output, or work performed by a piece of equipment, to the amount of energy input.

Question 2

Explain cooling capacity.

Answer 2

Equipment’s maximum cooling power output under specified conditions.

Question 3

Explain heating capacity.

Answer 3

equipment’s maximum heating power output under specified conditions.

Question 4

In HVAC systems, how are minimum efficiency ratings established?

Answer 4

by energy type, equipment category and size, or capacity category.

Question 5

AFUE

Answer 5

Annual Fuel Utilization Efficiency (%)
Equation: AFUE (%) = Energy output (Btu)/Energy input (Btu)
Definition: a thermal efficiency measure of combustion equipment like furnaces and boilers.
-ratio of useful energy output to energy input (Btu, kWh, J etc)
-higher %, higher efficiency
*condensing types are usually between 90 and 99 percent AFUE

Question 6

COP

Answer 6

Coefficient of Performance (COP)

Equation: COP = power output (W)/power input (W)

Ratio of a system’s power output to its power input. IN another way, it is the useful heating or cooling provided, compared to the work (energy) required.

Dimensionless quantity, and instantaneous unit because compares power, rather than energy

Air source heat pump has a lower COP (less efficient) at lower outdoor temperatures

Atypical COP is always higher than 1.

Question 7

HSPF

Answer 7

Heating Seasonal Performance Factor (HSPF)

• Applies to heat pumps.
• It is the ratio of the heating energy output (in Btu) to the electrical energy input (in watt-hours) (including supplementary electric heat) calculated over a full heating season.

equation:
HSPF[Btu/Wh] = seasonalheatenergyoutput /electricalinputseasonal

Question 8

EER

Answer 8

Energy Efficiency Ratio (EER)

• ratio of the cooling energy output ( in Btu) to the electrical energy input (in watt-hours)
• measure of energy performance for cooling equipment and heat pump systems. More specifically, it is the steady-state rate of heat energy removal (ie cooling capacity) by the equipment measured in Btu/h divided by the steady-state rate of energy input to the equipment measured in watts at specified temperatures.
• this is also a unitless value

Question 9

SEER

Answer 9

Seasonal Energy Efficiency Ratio (SEER):

• the ratio of cooling energy output (in Btu) to the electrical input energy (in watt-hours) calculated over a full cooling season
• SEEr is a unitless value representing the energy performance of a system over a season when outdoor temperature varies
• cooling equipment efficiency varies with operating conditions
• manufacturers make EER of COP measurements by applying various indoor and outdoor temperature and then calculate the SEER

Question 10

What is a Btu?

Answer 10

an imperial unit of energy equal to 1,055.96 joules. it is the amount of energy needed to raise the temperature of one pound of water by one degree Fahrenheit.

Question 11

What is Energy Factor(EF)?

Answer 11

EF is used to compare the energy conversion efficiency of residential appliances and equipment whose power output is 75,000 Btu or less. The EF is currently used for rating the efficiency of wate heaters, dishwashers, washing machine and dryers.