question: Why do bunker freezers still work in grocery stores even though they have no lids to trap cold air inside?
comment: 1. Cold air sinks while warm air rises, so unless there's a strong breeze it's not really going anywhere. 2. Some of them generate an artificial recirculating cold breeze (an "air curtain") to further limit unwanted air flow.
passages: In colder climates, where winter temperatures regularly drop below freezing, then "frost coils" or "pre-heat" coils are often employed as a first stage of air treatment to ensure that downstream filters or chilled water coils are protected against freezing. The control of the frost coil is such that if a certain off-coil air temperature is not reached then the entire air handler is shut down for protection.
  
  Section::::Components.:Humidifier.
  
  Humidification is often necessary in colder climates where continuous heating will make the air drier, resulting in uncomfortable air quality and increased static electricity. Various types of humidification may be used:
   Frost-free refrigerators, including some early frost free refrigerator/freezers that used a cold plate in their refrigerator section instead of airflow from the freezer section, generally don't shut off their refrigerator fans during defrosting. This allows consumers to leave food in the main refrigerator compartment uncovered, and also helps keep vegetables moist. This method also helps reduce energy consumption, because the refrigerator is above freeze point and can pass the warmer-than-freezing air through the evaporator or cold plate to aid the defrosting cycle.
   Section::::Water coil.
  
  The water coil freeze stat performs a similar function to the air coil freeze stat, but is used on a different type of HVAC system. Its function is to keep the freon-to-liquid heat exchanger (commonly called "liquid coils") from freezing.
   Replacing existing air conditioning systems with ice storage offers a cost-effective energy storage method, enabling surplus wind energy and other such intermittent energy sources to be stored for use in chilling at a later time, possibly months later.
  
  Section::::Air conditioning.
   The purpose of an air coil freeze stat is to keep the refrigerant-to-air heat exchanger (commonly called "air coils") from freezing. This kind of freeze stat is typically used for heating coils which are exposed to outside air and is usually installed on the supply air side of the coil. To accomplish this, they typically shut down the flow of outside air to a mixing box when the temperature reaches a predetermined setpoint. The setpoint for air coil freeze stats is typically about 12°C which is approximately when the dew point temperature of the air starts to drop below freezing point.
   Section::::Parallel terminal systems.
  
  For a typical DOAS ventilation system, the outside air system can accommodate around 0-30% of the space sensible load. In order to create a comfortable indoor environment, the balance of the space sensible loads must be accommodated by many other optional equipment choices as follows:
  
  BULLET::::- Radiant ceiling panels
  
  BULLET::::- A parallel all air variable-air-volume (VAV) systems
  
  BULLET::::- Packaged unitary water source heat pumps
  
  BULLET::::- Variable Refrigerant Flow (VRF) systems
  
  BULLET::::- Fan coil units
  
  Section::::Parallel terminal systems.:Radiant system.
   Free cooling systems can have very high efficiencies, and are sometimes combined with seasonal thermal energy storage so that the cold of winter can be used for summer air conditioning. Common storage mediums are deep aquifers or a natural underground rock mass accessed via a cluster of small-diameter, heat-exchanger-equipped boreholes. Some systems with small storages are hybrids, using free cooling early in the cooling season, and later employing a heat pump to chill the circulation coming from the storage. The heat pump is added-in because the storage acts as a heat sink when the system is in cooling (as opposed to charging) mode, causing the temperature to gradually increase during the cooling season.
   Section::::Episodes.:6. "Footsteps in the Snow".
   Due to the low temperature, ULT freezer consume high amounts of electric energy per day. Depending on the volume of the freezer, the opening frequency of the users as well as the number of samples, the energy consumption starts from ca. 11 KWh/ day and higher. To reduce the energy consumption, the insulation should be as efficient as possible. Additional inner doors reduce the loss of temperature when opening the main door. Icing within the ULT freezer should be reduced to a minimum.
   Air convection heating systems have been in use for over a century. Older systems rely on a passive air circulation system where the greater density of cooler air causes it to sink into the furnace area below, through air return registers in the floor, and the lesser density of warmed air causes it to rise in the ductwork; the two forces acting together to drive air circulation in a system termed 'gravity-fed'. The layout of these 'octopus’ furnaces and their duct systems is optimized with various diameters of large dampered ducts.
   The simplest and lowest cost open-cycle cooling systems, known as swamp coolers in the south-west United States, do not even need power for a compressor, merely a blower fan, so humidified cooled air is simply vented into the living space. Portable free-standing units can be obtained at discount stores for less than $200. However, if these systems are improperly implemented the drawbacks are multiple and severe.
   BULLET::::- Better temperature management.
  
  Section::::Disadvantages.
  
  BULLET::::- The system can be more expensive to run when usage is high and if the fan continues or starts to run when the door is opened.
  
  BULLET::::- A thermal cutout safety device is required to prevent overheating of the heating element.
  
  BULLET::::- Increased electrical and mechanical complexity compared to a basic upright freezer or freezer chest, making it more prone to component failure.
   The furnace in utility core supplies heat to the main space through heating ducts, which are arranged along the base of the glass walls for maximum efficiency. During the winter the lack of overhangs provides maximum passive heat gain, and use of the original Koolshade panels was meant to minimize excessive heat gain in the summer.
   In the 1890s gold miners in Australia developed the Coolgardie safe, based on the same principles.
   Within these refrigerators and freezers, vaccines are also compromised through improper use of the door gasket to feed cables from data loggers and thermometers, allowing excess warm air in, and cold air out of the refrigerator or freezer. Over time this causes the compressor to work harder and eventually leads to failure. This can be remedied by using probe access ports, found on most clinical refrigerators and freezer. These are easy to open up and drastically reduce air intake and loss from inside the units.
  
  Section::::Solar powered vaccine refrigerators.
   In instances where noise reduction and moisture containment around a conveyorized air knife installation becomes important, some manufacturing facilities have installed air knives within an enclosure. These enclosures keep water contained, reduce the amount of air knife noise and even eliminate any liquid that could create safety concerns.
  
  Section::::Basic design features.
  
  Section::::Basic design features.:Compressed air-powered air knives.
   Cold hole
  
  In ad hoc outdoor shelters, a cold hole is the practice of deliberately creating a space for the cold air to gather, at a lower level than where people sleep.
   BULLET::::- Determining the supply air humidity ratio for each space
  
  BULLET::::- Typically, the design supply air dry bulb temperature will equal the required supply air dew point temperature)
  
  BULLET::::- Using energy recovery to move exhaust air heat back to the DOAS unit (during heating seasons)
   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.
   In order to maintain indoor air quality, air handlers commonly have provisions to allow the introduction of outside air into, and the exhausting of air from the building. In temperate climates, mixing the right amount of cooler outside air with warmer return air can be used to approach the desired supply air temperature. A mixing chamber is therefore used which has dampers controlling the ratio between the return, outside, and exhaust air.
  
  Section::::Components.:Blower/fan.
   Inside the freezer, air is circulated by means of one or more fans. In a typical design cold air from the freezer compartment is ducted to the fresh food compartment and circulated back into the freezer compartment. Air circulation helps sublimate any ice or frost that may form on frozen items in the freezer compartment.
  
  Instead of the traditional cooling elements being embedded in the freezer liner, auto-defrost elements are behind or beneath the liner. This allows them to be heated for short periods of time to dispose of frost, without heating the contents of the freezer.
   Freezer units are used in households and in industry and commerce. Commercial refrigerator and freezer units were in use for almost 40 years prior to the common home models. The freezer-on-top-and-refrigerator-on-bottom style has been the basic style since the 1940s, until modern refrigerators broke the trend. A vapor compression cycle is used in most household refrigerators, refrigerator–freezers and freezers. Newer refrigerators may include automatic defrosting, chilled water, and ice from a dispenser in the door.
   BULLET::::- Storage of high value items
  
  BULLET::::- Archives
  
  BULLET::::- Freezer and cold storage
  
  BULLET::::- Large warehouses
  
  BULLET::::- Paper mills
  
  BULLET::::- Heritage applications
  
  BULLET::::- Telecom
  
  BULLET::::- Electrical substation
  
  BULLET::::- Utilities
  
  BULLET::::- Document Storage
  
  BULLET::::- High-bay Warehouses
  
  The reduction of artifact degradation and food deterioration is a plus for applications like food warehouses, storage and archives.
  
  The inherent simplicity of hypoxic air systems facilitates integration of sustainable building design and fire protection engineering.
  
  Section::::Effects on health.
   BULLET::::- A refrigerating appliance is required to maintain temperatures inside its compartments within specified limits, and to operate (including defrosting) in a specified ambient temperature while using at most a specified amount of electricity; the energy use allowed varies according to volume, number of doors, the function of the various compartments and other parameters. This graph shows the dramatic reduction in electricity use in U.S. refrigerators following the introduction of a series of first California then U.S. MEPS starting in the mid-1970s:
   BULLET::::- Because radiant loads are treated directly and air motion in the space is at normal ventilation levels, comfort levels can be better than those of other air-conditioning systems
  
  BULLET::::- Meet the requirement of supply quantities for ventilation and dehumidification
  
  BULLET::::- Due to the reduced outdoor air quantities, the DOAS system can be installed with smaller duct system
  
  BULLET::::- Radiant ceiling cooling panels can eliminate wet surface cooling coils and reduce the potential for septic contamination
  
  BULLET::::- The automatic sprinkler system piping can be applied into radiant ceiling cooling panel systems
  
  The main disadvantage is related to higher initial costs.
  
presuppositions: A freezer keeps things cold because it has a lid. Freezers need to trap cold air with a lid to work.
corrections: A freezer does not need a lid to keep things cold. Cold air sinks, so bunker freezers do not need a lid to work.
raw_presuppositions: A freezer keeps things cold because it has a lid. Freezers need to trap cold air with a lid to work.
raw_corrections: A freezer does not need a lid to keep things cold. Cold air sinks, so bunker freezers do not need a lid to work.