question: Why does ventilated air not become warmer?
comment: Theoretically it is, but the change is almost unmeasurable. Make that fan do 30000 rpms and you could measure it. Pressure changes would have more of an effect on air temperature than friction.
passages: Throughout the cooling season, the system works to cool and dehumidify the incoming, outside air. This is accomplished by the system taking the rejected heat and sending it into the exhaust airstream. Subsequently, this air cools the condenser coil at a lower temperature than if the rejected heat had not entered the exhaust airstream. During the heating seasons, the system works in reverse. Instead of discharging the heat into the exhaust airstream, the system draws heat from the exhaust airstream in order to pre-heat the incoming air. At this stage, the air passes through a primary unit and then into a space. With this type of system, it is normal, during the cooling seasons, for the exhaust air to be cooler than the ventilation air and, during the heating seasons, warmer than the ventilation air. It is for this reason the system works very efficiently and effectively. The coefficient of performance (COP) will increase as the conditions become more extreme (i.e., more hot and humid for cooling and colder for heating).
   While natural ventilation eliminates electrical energy consumed by fans, overall energy consumption of natural ventilation systems is often higher than that of modern mechanical ventilation systems featuring heat recovery. Typical modern mechanical ventilation systems use as little as 2000 J/m3 for fan operation, and in cold weather they can recover much more energy than this in the form of heat transferred from waste exhaust air to fresh supply air using recuperators.
  
  Ventilation heat loss can be calculated as: theta=Cp*rho*dT*(1-eta).
  
  Where:
  
  Theta is ventilation heat loss in W
  
  Cp is specific heat capacity of air (~1000 J/(kg*K))
   Section::::Environmental impacts.:Greenhouse gases.
   Section::::Working principle.
   reaching a relatively high velocity before rising due to heat exchange with heat sources (e.g., occupants, computers, lights). Absorbing the heat from heat sources, the cold air becomes warmer and less dense. The density difference between cold air and warm air creates upward convective flows known as thermal plumes. Instead of working as a stand-alone system in interior space, displacement ventilation system can also be coupled with other cooling and heating sources, such as radiant chilled ceilings or baseboard heating.
  
  Section::::History.
   Below the operating temperature, the liquid is too cold and cannot vaporize into a gas. Above the operating temperature, all the liquid has turned to gas, and the environmental temperature is too high for any of the gas to condense. In other words, whether too high or too low, thermal conduction is still possible through the walls of the heat pipe, but at a greatly reduced rate of thermal transfer.
   BULLET::::- Stack ventilation - Cross ventilation is an effective cooling strategy, however, wind is an unreliable resource. Stack ventilation is an alternative design strategy that relies on the buoyancy of warm air to rise and exit through openings located at ceiling height. Cooler outside air replaces the rising warm air through carefully designed inlets placed near the floor.
  
  One specific application of natural ventilation is night flushing.
  
  Section::::Modulation and heat dissipation techniques.:Night flushing.
   We use our nose and throat as a regenerative heat exchanger when we breathe. The cooler air coming in is warmed, so that it reaches the lungs as warm air. On the way back out, this warmed air deposits much of its heat back onto the sides of the nasal passages, so that these passages are then ready to warm the next batch of air coming in. Some animals, including humans, have curled sheets of bone inside the nose called nasal turbinates to increase the surface area for heat exchange.
  
  Section::::Types of regenerators.:Cryogenics.
   When a parcel of air expands, it pushes on the air around it, doing work (thermodynamics). Since the parcel does work but gains no heat, it loses internal energy so that its temperature decreases. The process of expanding and contracting without exchanging heat is an adiabatic process. The term "adiabatic" means that no heat transfer occurs into or out of the parcel. Air has low thermal conductivity, and the bodies of air involved are very large, so transfer of heat by conduction is negligibly small.
   Secondly there a "diffusion" process. The air arriving in the alveoli has a higher concentration of oxygen than the “stale” air in the alveoli. The increase in oxygen concentration creates a concentration gradient for oxygen between the air in the alveoli and the blood in the capillaries that surround the alveoli. Oxygen then moves by diffusion, down the concentration gradient, into the blood. The other consequence of the air arriving in alveoli is that the concentration of carbon dioxide in the alveoli decreases. This creates a concentration gradient for carbon dioxide to diffuse from the blood into the alveoli, as fresh air has a very low concentration of carbon dioxide compared to the blood in the body.
   Section::::Environmental impacts.:Energy consumption.
   Ventilative cooling requirements in regulations are complex. Energy performance calculations in many countries worldwide do not explicitly consider ventilative cooling. The available tools used for energy performance calculations are not suited to model the impact and effectiveness of ventilative cooling, especially through annual and monthly calculations .
  
  Section::::Case studies.
   Both of these convection processes immediately begin to slow down, and eventually stop, as soon as the burners turn off.
  
  Section::::Efficiency.
   In many post-occupancy comfort studies overheating is a frequently reported problem not only during the summer months but also during the transitions periods, also in temperate climates.
  
  Section::::Potentials and limitations.
   If the adiabatic lapse rate is "lower" than the ambient lapse rate, an air mass displaced upward cools "less" rapidly than the air in which it is moving. Hence, such an air mass becomes "warmer" relative to the atmosphere. As warmer air is less dense, such an air mass would tend to continue to rise.
   The total cooling power of the unit is limited by the fact that neither coolant nor air can be recirculated. If the cooling unit does not have a supply of fresh dry air and the waste air is not effectively vented, stagnant humid air will make the space more uncomfortable than if it were merely ventilated.
  
  An additional limitation of such systems would be that if the air outside is already humid, cooling power is severely limited. This is why such units are not found in areas of frequent and high humidity, such as the south-east United States.
   Ventilation should be considered for its relationship to "venting" for appliances and combustion equipment such as water heaters, furnaces, boilers, and wood stoves. Most importantly, the design of building ventilation must be careful to avoid the backdraft of combustion products from "naturally vented" appliances into the occupied space. This issue is of greater importance in new buildings with more air tight envelopes. To avoid the hazard, many modern combustion appliances utilize "direct venting" which draws combustion air directly from outdoors, instead of from the indoor environment.
   Fig 5 shows the typical behaviour of the dynamic insulation temperature profile when the air flows in the same direction to the conductive heat flow (pro-flux). As air at room temperature flows outwards with increasing speed the temperature profile becomes increasingly more curved. On the warm side of the insulation the temperature gradient becomes increasingly horizontal as the warm air prevents the insulation cooling down in the linear way that would occur with no air flow. The conductive heat loss into the wall is very much less than that for conventional insulation. This does not mean that the transmission heat loss for the insulation is very low.
   Annex 62 ‘ventilative cooling’ was a research project of the ‘Energy in Buildings and Communities Programme (EBC)’ of the International Energy Agency (IEA), with a four-year working phase (2014–2018).
   It is likely that Robert Stirling's air engine of 1818, which incorporated his innovative "Economiser" (patented in 1816) was the first air engine put to practical work. The economiser, now known as the regenerator, stored heat from the hot portion of the engine as the air passed to the cold side, and released heat to the cooled air as it returned to the hot side. This innovation improved the efficiency of Stirling's engine and should be present in any air engine that is properly called a Stirling engine.
   Air movement will increase sweat evaporation, which cools the body. But in extreme heat – when the blown air is warmer than the body's temperature – it will increase the heat stress placed on the body, potentially speeding the onset of heat exhaustion and other detrimental conditions. The American Environmental Protection Agency (EPA) discourages people from using fans in closed rooms without ventilation when the heat index is above . The EPA does, however, approve of using a fan if a window is open and it is cooler outside, or when the heat index in a closed room is lower.
   Since buildings are not totally sealed (at the very minimum, there is always a ground level entrance), the stack effect will cause air infiltration. During the heating season, the warmer indoor air rises up through the building and escapes at the top either through open windows, ventilation openings, or unintentional holes in ceilings, like ceiling fans and recessed lights. The rising warm air reduces the pressure in the base of the building, drawing cold air in through either open doors, windows, or other openings and leakage. During the cooling season, the stack effect is reversed, but is typically weaker due to lower temperature differences.
   A newer version from Nibe Sweden the F730 takes in additional air from outdoors to the above process - this is a more powerful type of EAHP with an inverter controlled compressor. Out put from the heat pump can vary from 1.1 to 6 kW and the discharged air from this unit can be as low as -15 °C
  
  Section::::NIBE.
  
  F200P 
  
  BULLET::::- Discontinued
  
  F360P 
  
  BULLET::::- Discontinued
  
  F205 F370 F470
  
  F750
  
  F730
  
  Section::::Issues.
   Air is circulated through ductwork, which may be made of sheet metal or plastic "flex" duct, and is insulated or uninsulated. Unless the ducts and plenum have been sealed using mastic or foil duct tape, the ductwork is likely to have a high leakage of conditioned air, possibly into unconditioned spaces. Another cause of wasted energy is the installation of ductwork in unheated areas, such as attics and crawl spaces; or ductwork of air conditioning systems in attics in warm climates.
  
  Section::::Home furnaces.
   The simplest VAV system incorporates one supply duct that, when in cooling mode, distributes supply air at a constant temperature of approximately . Because the supply air temperature is constant, the air flow rate must vary to meet the rising and falling heat gains or losses within the thermal zone served.
  
presuppositions: Ventilated air does not become warmer. Ventilated air does not become warmer/.
corrections: Ventilated air does become warmer, but the change is almost unmeasurable. Ventilated air does become warmer, the change is just not measurable.  
raw_presuppositions: Ventilated air does not become warmer. Ventilated air does not become warmer/.
raw_corrections: Ventilated air does become warmer, but the change is almost unmeasurable. Ventilated air does become warmer, the change is just not measurable.  