What is ACH infiltration?
Infiltration measures The air exchange rate is also known as air changes per hour (ACH). ACH is the hourly ventilation rate, divided by the building volume. It can be calculated by multiplying the building’s CFM by 60, and then dividing by the building volume. (
What are heat infiltration losses?
OVERVIEW. Heat loss from infiltration is uncontrolled air leakage through joints in the construction and cracks around windows and doors. Infiltration is caused by wind and stack-driven pressure differentials, which prompt air movement within the building envelope.
What is infiltration process?
Infiltration is the process of water entry into the soil through the earth’s surface. The water at the soil surface can originate from rain, snowmelt or anthropogenic activities (e.g. to regulate groundwater formation by artificial infiltration).
What do you know about infiltration losses?
Infiltration is air movement into and out of a greenhouse through cracks and small openings in the shell of the building. New construction greenhouses can range from 0.5 to 1.5 air exchanges per hour while old construction glass glazed greenhouses can range from 1 to 4 air exchanges per hour.
How do you calculate heat loss due to ventilation?
The energy required to raise one cubic metre of air through one kelvin is 0.33 watt-hours, i.e. its heat capacity per cubic metre is 0.33 Wh m–3 K−1. Thus the total ventilation heat loss, Qv , will be: Qv = 0.33 × n × V × ΔT watts.
What is the difference between infiltration and exfiltration?
Air infiltration is the movement of air into a building, whereas air exfiltration is the movement of air out of a building. Air flows into or out of a building because of pressure differences between the internal and external environments of the building.
What is the difference between infiltration and ventilation?
Infiltration is the unwanted and unintentional flow of air through a building’s fabric. Ventilation is the deliberate movement of air to remove contaminants such as water vapour, airborne chemicals (VOCs), CO2, NOx, and odours from an indoor environment, and to keep everything feeling ‘fresh’.
What is sensible heat gain?
When an object is heated, its temperature rises as heat is added. The increase in heat is called sensible heat. Similarly, when heat is removed from an object and its temperature falls, the heat removed is also called sensible heat. Heat that causes a change in temperature in an object is called sensible heat.
What is the minimum requirement for fresh air?
The minimum fresh air requirement of 8 to 10 l/s per person typically adopted in mechanically ventilated spaces is supported by a variety of sources (refer to section 2). Fresh air requirements for naturally ventilated spaces are treated differently (refer to section 3).
What is the difference between infiltration and ventilation quizlet?
infiltration is air that leaks, while ventilation is drawn in on purpose.
What is latent heat gain quizlet?
PLAY. Match. Only $2.99/month. What is latent heat? Quantity of heat gained or lost per unit of mass as a substance undergoes a change of state.
What does amplification mean in indoor air quality terms?
What does amplification mean to in indoor air quality terms. a contaminant’s ability to grow and spread. What is the odorant commonly used in natural gas? Mercaptan. VOCs are.
What is difference between sensible heat and latent heat?
Latent and sensible heat are types of energy released or absorbed in the atmosphere. Latent heat is related to changes in phase between liquids, gases, and solids. Sensible heat is related to changes in temperature of a gas or object with no change in phase.
How do you calculate latent heat?
Latent heat calculation The specific latent heat is different for solid to liquid transition and liquid to gas transition. For example, if we want to turn 20 g of ice into water we need Q = 20 g * 334 kJ/kg = 6680 J of energy. To turn the same amount of water into vapor we need Q = 45294 J .
What does latent heat depend on?
Latent heat is an intensive property measured in units of J/kg. Both Lf and Lv depend on the substance, particularly on the strength of its molecular forces as noted earlier. Lf and Lv are collectively called latent heat coefficients.
Does latent heat depend on temperature?
Latent heat, energy absorbed or released by a substance during a change in its physical state (phase) that occurs without changing its temperature. While the ice is absorbing latent heat, its temperature is not changing.
Does latent heat change with pressure?
As pressure on molecules increases they require more heat to overcome the pressure force acting or to escape and thus latent heat required is more. Thus as presure increases at 100 degree latent heat of vapourisation also increases while as pressure increases latent heat of condensation decreases.
How does latent heat show up on a phase diagram?
Latent heat is changing phase, and when a change in phase is accomplished at constant pressure temperature is constant. On the phase diagram, latent heat shows up as a “thermal plateau” where the graph is a flat line for a brief portion.
Why latent heat of steam decreases with increase in pressure?
The heat energy (enthalpy of evaporation) needed by the water at higher pressure to change it into steam is actually less than the heat energy required at atmospheric pressure. This is because the specific enthalpy of evaporation decreases as the steam pressure increases.
What is the effect of increasing pressure on the latent heat of steam?
Increasing the pressure increases the temperature of the phase change, and increases the amount of energy the water/steam can carry. At pressures higher than atmospheric, more heat must be added to water (sensible heat) before it can turn to steam.
What is specific latent heat of steam?
The temperature of the hot water leaving a steam trap will be at or just below the water boiling point corresponding to the pressure. As the latent heat of steam at atmospheric pressure is 2257 kJ/kg the amount of flash steam produced will be 299/2257 = 0.133 kg/kg of condensate.
When water is heated without rise of temperature it consumes?
When water is heated, latent heat of vaporisation is consumed to overcome the intermolecular forces of attraction at a constant temperature.
Does steam temperature increase with pressure?
When water is heated at atmospheric pressure, its temperature rises until it reaches 212°F, the highest temperature at which water can exist at this pressure. Additional heat does not raise the temperature, but converts the water to steam.
Can Steam be hotter than 212 degrees?
Q: Is it true that water (steam and ice) can not get hotter than 212 degrees and colder than 32 degrees? It is not true that water can only get up to 212 degrees and as cold as 32 degrees. After water changes from a liquid to a gas (at 212 degrees Fahrenheit) it can actually heat up much hotter than that.