Air Conditioning Glossary


Absolute Humidity

The ratio of the mass of water vapor contained in a volume of air to the total mass of that volume of air. The units are kg/kg.

Absolute Pressure

The pressure measured referenced to the pressure of an complete vacuum as 0. Units are interms of kg/cm2 abs or kg/cm2 absolute. Atmospheric pressure in terms of absolute pressure would be 1.03 kg/cm2.Absolute Pressure = Gauge Pressure + Atmospheric Pressure (1.03 kg/cm2)

Absolute Temperature

Absolute temperature is a temperature in which absolute zero is when the motion of the material particles stops (as considered in the thermodynamical sense), and a is scale applied that is the equivalent to the Celsius scale. The freezing point of water in terms of absolute temperature is 273 K (Kelvin).

Anemostat Diffuser

A ceiling-mounted outlet with several cone-shaped blades inside. Allows airflow that is blown into a room to induce and mix with the existing room air.

Air Curtain

An air curtain is equipment installed at openings such as entrances and entrances of buildings to form a thick layer of airflow in order to block the ingress of outside air, foreign matter, and dust. It is used to prevent internally cooled and heated air from leaking out in buildings with many people, and is installed at the entrance of packing material storage and raw material warehouses in food factories and pharmaceutical factories, etc. In addition, it prevent foreign bodies such as mosquitoes, flies and insects from entering warehouses.

Air Handling Unit

A relatively large-capacity air conditioner that integrates a hot and cold water coil, humidifier, drain pan, blower, and air filter. Since each device can be combined according to the required conditions of the blown air, it is also used for air conditioning that requires strict temperature and humidity control.

Air Supply Opening (Outlet)

An opening in a wall or other surface to take in air. In case of natural ventilation, the Building Standards Law stipulates that they be installed at a height of less than half the ceiling height.

Aspect Ratio

Mainly it specifies the ratio of the long side to the short side of a duct outlet, intake grille frame, or rectangular duct frame.

A-type Contact

A term representing the contact structure of a relay or similar device, and refers to a structure in which the contacts are normally open (open circuit) when the relay is not operating (when it is not energized). The contacts are closed (closed circuit) when the relay is energized. Also referred to as "normally-on" or NO.


Background Noise

When a specific sound is considered as a target in a certain place, noise at the place when there is no target sound is referred to as background noise with respect to the target sound. When examining the noise of air conditioning equipment in facilities such as halls and studios, it refers noise when the air conditioning equipment is stopped and in the absence of people. Special background noise is noise that enters from the outside, internally generated noise other than air conditioning equipment, and the like. Displayed in dB (A).

Bell Mouth

The point where the speed of the gas or liquid is increased by rapidly squeezing the fluid is called a bell mouth. The bell mouth is the intake port of an axial blower.

Bioclean Room

A cleanroom for microoganisms. The structure is the same as that of an industrial cleanroom, but the main purpose is to control dust-borne bacteria, and so the room is devised so that it can be sterilized. A biological cleanroom.


A type of centrifugal fan that compresses air and other gases. The pressure capacity can be 1 to 20 mH₂O, and it is used for pumping air, gas, etc., in factories and the like.


Also referred to as a secondary refrigerant, brine is a liquid used in indirect cooling systems that circulates through the evaporator of a refrigerator and to a place to be cooled, transferring heat to the evaporator.

Butterfly Valve

A valve in which a disk-shaped valve element rotates and opens and closes in a cylindrical valve enclosure, operated from a drive shaft along the diameter of the valve element.


Carbon Monoxide

An odorless and colorless gas. Carbon monoxide is generated when fuel lacks oxygen during combustion. Even a small amount of this gas is harmful to the human body. The indoor environmental standard is 10 ppm (0.001%) or less, and the environmental standard for air pollution is 10 ppm or less per hour as a daily average, or 20 ppm or less per hour as an 8-hour average.


A phenomenon whereby, due to the increasing flow velocity and the forming of vortices, the pressure in a flowing liquid will drop locally, and when near its saturated vapor pressure, steam and many bubbles will form. When the bubbles that form move to a place where the pressure is high, they collapse instantaneously and generates an impact pressure. This erodes nearby solid walls with severe vibration and noise.

Chemical Filter

A filter used for removing chemical pollutants.


This system increases energy efficiency by utilizing electricity generated by burning fuel as well as utilizing recovered waste heat.

Cold Draft

Draft generally refers to a flow of air, and refers to airflow that causes discomfort to the human body. A flow of air that gives an unpleasant sensation of cold.

Comfortable Temperature

A temperature and humidity condition, within a certain range that depends on the season, in which many people feel comfortable. The average comfortable temperature in winter is 18.9 °C. While under this effective temperature, many people feel comfortable when the relative humidity is in the range of 30 to 70%.


The process of functionally planning, constructing, and commissioning the functionally of each equipment system, and confirming that reliable operation and maintenance can be undertaken according to the design intent (under ASHRAE guidelines). An effort by a design/construction company and a neutral third party to prove whether the building equipment system is performing as required by the entity who ordered the building. Also, performance verification by a third party in which the third party objectively checks for mistakes or omissions that the installer has overlooked and also to realize optimization of the equipment system. There are three stages of commissioning. Design performance verification which is verification of the design details; construction performance verification, which is verification of the construction process and re-verification within one year after completion; and operation performance verification, which is evaluation of equipment system suitability, environmental and energy performance results, etc.


A device that converts AC power to DC power. An inverter is a device that rectifies an alternating current source into direct current and then converts that direct current power into alternating current of an arbitrary alternating frequency. A rectifier circuit for converting AC power to DC is called a converter.


Degree of Superheat

In a gas, it is the number of degrees higher in temperature than the saturation temperature under a certain pressure. In the refrigeration cycle, it is the difference between the evaporation temperature (saturation temperature) and the temperature at the evaporator outlet. The symbol is written as "deg".A superheat of 5 deg means that the temperature from the evaporator inlet to the outlet is constant at, for example 7 °C, and then at the outlet the steam is superheated by 5 °C and becomes superheated steam of 12 °C.

Derivative Action

A control action that gives a manipulated variable in proportion to the rate (speed) of deviation. The derivative prevents the deviation from becoming too large and is used in combination with the P and PI operations. It is also referred to as the D action.

Design Specification

This refers to a questions and answers document that addresses particular specifications, drawings, common specifications, and site descriptions.

Dew Point

Dew point is the temperature such that when air is cooled to that temperature, the contained water vapor becomes liquid (mist).The maximum amount of water vapor that air can contain at a certain temperature is called the amount of saturated water vapor, and the water vapor exceeding this limit (saturated state) appears as fog. The temperature when this occurs is the dew point (or dew point temperature).

Dew Point Control

This is a control method used to more accurately control the relative humidity in a constant temperature and humidity device. First the outside temperature corresponding to the predetermined indoor temperature and humidity is controlled. Then an amount of reheating is applied to make up for any shortage of the indoor sensible heat load.

Discomfort Index

A numerical value that expresses the state of air in which humans feel uncomfortable. Discomfort Index = (dry-bulb temperature + wet-bulb temperature) x 0.72 + 40.6. Generally 70 or lower is considered comfortable, 75 or lower is moderate, and 80 or higher is unpleasant.


Generally speaking this is the flow of air due to differences in pressure. It refers to the flow of air or gas that occurs in hot air pipes, chimneys, heaters, and indoor spaces. In the case of a heater, it can be said that it is the rising tendency caused by the difference between the specific gravity of the combustion-heated high-temperature exhaust gas and the specific gravity of the normal temperature air being supplied. It also refers to airflow uncomfortable to the human body, and sometimes refers to a drafty wind or natural convection of cold wind from the window in winter.

Drying Operation

This means dehumidification operation.① If you only want to dehumidify a room without lowering the room temperature, then use a device equipped with a reheater separate from the evaporator. Once the air is cooled down in the room, the temperature and humidity will be reduced, at which point the temperature is raised using a reheater. This will cause the humidity to drop without a drop in temperature.② In many cases, dry operation through control of a fan is used to achieve the same effect as "dry operation". If the fan is controlled and blows the air slowly at the lowest speed, the room temperature will gradually decrease and at the same time, the humidity will increase.

Dynamic Pressure

Dynamic pressure or velocity pressure is the air in the duct or the liquid in the pipe that has a pressure generated by wind pressure or flow velocity, in addition to static pressure. The units are the same as with static pressure.


Effective Temperature

Temperature perceived by the human body. This is different from air temperature. The effects will be felt depending on the temperature, humidity, and wind speed, etc.


The ratio of output energy to input energy shows how much input energy is effectively used as work. When referring to the efficiency of a refrigeration device, the ratio of the work supplied to the device to the work that the device can output is expressed as a percentage.


A device that removes water droplets by preventing the scattering of water droplets that accompany the air flow in air conditioners and cooling towers. Usually the water droplets are separated out by utilizing their inertial force in a zigzag-folded iron or resin molded plate structure.


Refers to the total energy (total amount of heat) stored inside an object. It is expressed as: Enthalpy (H) = Internal Energy (E) + { Pressure (P) x Volume (V) }. Usually expressed as an amount per kg, with the units being kcal/kg.


Fan Coil

A small air conditioner that discharges temperature-controlled air, and consists of a fan (blower), heat exchanger, and filter. It cannot perform ventilation or humidity control.

Fan Filter Unit (FFU)

A device with a built-in filter and blower that can supply clean air simply by connecting to a power supply.

Fan Laws (Affinity Laws)

The fan speed is changed in order to change the characteristics of the fan. But if the amount of rotation is within ±20%, then the characteristics of the fan will change according to the following proportional laws. These laws are what are known as the fan laws. ① The volume of air is proportional to the fan speed. ② The wind pressure (total pressure, static pressure, power) is proportional to the square of the fan speed. ③ The shaft power is proportional to the cube of the fan speed. ④ When the fan speed and air volume are constant, the wind pressure and power are proportional to the density of the air.

Feedback Control

A control method in which a result controlled by a control signal output from a control system is compared with a set (target) value and a correction operation is performed so as to match that set (target) value.

Feed-forward Control

A control method whereby, when a disturbance to a control system is detected, the required correction operation for the disturbance is performed such that it doesn't affect the control system.

FRP (Fiber Reinforced Plastic)

Plastic reinforced with fiber. A typical composite material made by mixing fibers with plastic. Generally the fiber used is glass fiber. FRP is used for polyethylene bathtubs, water reservoirs, elevated water tanks, etc.


General Specification

Part of the overall specifications, a specifications document that specifies shared instructions with the construction site ahead of time. Also known as standard specifications.

Greenhouse Effect

A phenomenon in which gas and air pollutants in the atmosphere absorb infrared radiation that dissipates heat from the ground surface to the outside (to space), preventing this infrared radiation from escaping outside the Earth and thereby increasing the Earth's temperature.


HACCP (Hazard Analysis and Critical Control Point)

This is a process management system that confirms places where harm may occur in the food manufacturing process and takes strict measures to prevent such harm in advance. Strict monitoring and control of individual steps in the process reduces the potential for such harm. The top priority in the HACCP system is to prevent chemical, physical and microbiological harm throughout the production process, all the way from the farm to the table. HACCP was first adopted in the 1960s by Pillsbury in the space development program to produce the safest and highest quality food for astronauts.

Hard PVC-Lined Steel Pipe for Water Supply

Water pipe used for plumbing made by lining a hard polyvinyl chloride resin (based on JIS K 6742 quality) on a black carbon steel pipe (JIS G 3452) or a galvanized steel pipe (JIS G 3442).

Heat Conductivity or Thermal Conductivity

Rate used to indicate the quality of heat conduction. Units used are kcal/(m⋅h⋅°C).The amount of heat is proportional to the heat transfer area, the temperature difference, and time with a certain proportionality constant, and is also inversely proportional to the distance over which the heat travels. It is this constant of proportionality.

Heat of Respiration

Fruits and vegetables continue respiration even after being harvested, and the heat generated by this respiration is released outside the body of the item as sensible heat. This heat is called heat of absorption.

Heat Pipe

A volatile liquid is sealed inside a pipe together with a special circulation device, thus extremely improving its heat conductivity. It is used for heat exchangers. The volatile liquid evaporates when one end is warmed and quickly causes the other end to reach a uniform temperature. When the evaporated liquid cools at the other end, it condenses into a liquid and returns to the initial end for re-circulation. A wick is usually installed inside the pipe so that the liquid can return easily.

Heat Transfer Coefficient

When a high temperature fluid (gas or liquid) is in contact with one surface of a solid wall and a low temperature fluid is in contact with the ground, heat is transferred from the high temperature fluid to the low temperature fluid through the solid wall. This phenomenon is referred to as heat flow, and the coefficient indicates the degree to which this occurs. It is also referred to as the "overall heat transfer coefficient".This rate has a uniform relationship between the thermal conductivity between the fluid and the wall and the thermal conductivity within the wall itself. The units are expressed in kcal/(m2⋅h⋅℃).

HEPA (High Efficiency Particulate Air) Filter

An air filter that has a particle capture rate of 99.97% or more for particles of 0.3 µm at the rated flow rate of the filter. It is an ultra-high performance filter used in all fields where air purification is required.

High Velocity Duct

Ducting for air conditioning with a wind speed of 15 m/s or higher inside the duct. A high-speed duct can greatly reduce the area inside the duct, and a spiral duct is used for its strength. However a drawback is that noise is easily generated, so a silencing box is required at the outlet.

Hot Gas Bypass

Hot gas bypass is a system whereby part of the compressed gas (hot gas) is led to the intake side in order to change the capacity of the refrigerating compressor to better match the load. This is a method for controlling the capacity of a small compressor that does not have an unloader va;ve.


When a control signal is used to perform a control operation, the control amount changes periodically and the control state does not stabilize.


Ice Thermal Storage Tank

A device that uses the state of ice to store cold.

Industrial Air Conditioning

As it refers to air conditioning used in the production process of various industries, animals and objects as the main targets rather than people. Therefore, the temperature and humidity conditions depend on the purpose and characteristics of the animal or thing, and are not significantly related to the season. Also, allowable ranges of temperature and humidity and cleanliness are determined, and accuracy is strictly required. Also sometimes referred to as "process air conditioning".

Instant Coupling

A coupling that can quickly connect an outdoor unit such as with a separate room air conditioner or small package air conditioner to the refrigerant circuit piping of the indoor unit. Tighten to 480 kg/cm2 using the specified torque wrench.

Integral Action

A control action whereby the controlled variable is calculated as the sum (area) of the product of the magnitude of the control deviation, and the time during which the deviation occurs, that is, the controlled variable is proportional to the magnitude of the integral value. Since the operation magnitude increases as long as there is a deviation, it is used in conjunction with the proportional operation as it has the effect of eliminating the offset generated by it.


Laminar Flow Cleanroom

A cleanroom that provides laminar airflow (uniform wind speed and uniform air streams) with minimal eddies in most areas of the space.

Latent Heat

The heat expended when a substance undergoes a change in state from a solid to a liquid or a liquid to a solid without undergoing a change in temperature. The heat of fusion, the heat of evaporation, and the heat of sublimation are collectively referred to as the latent heat of state change.


A wing-shaped baffle made of slender plates that are attached horizontally, vertically, or in a grid over the entire opening. There are fixed and variable types.


Masking or Surface Protection or Area Protection
("Curing" in Japanese)

Generally, in the area around a construction site or surfaces of materials and things should be covered in order to protect them from contamination. Such areas or items can be covered with sheets or paper, wrapped with masking tape, or enclosed in plywood. It also refers to measures to protect people and objects from hazards around dangerous work and damage at construction sites, or may also refer to facilities for that purpose.

Medium Temperature Air Conditioning

Environmental air conditioning in the temperature range of 10 to 25 °C. Used in food factories, delicatessens, backyards, etc. for temperature ranges where the growth of bacteria and mold is suppressed, and so that workers can work easily because it's not too cold.

MEPA (Medium Efficiency Particulate Air) Filter

A medium-performance filter that is mainly used for treating outside air in air conditioning systems and is used not only as a main filter but also as a form of protection for ULPA and HEPA filters.


Normally Closed (NC)

This refers to an operational function in which the valve opens when energized and it is fully closed when not energized. Also, form B contact.

Normally Open (NO)

This refers to an operational function in which the valve closes when energized and it is fully open when not energized. Also, form A contact.



When a control operation is performed that is dependent on a control signal (the actual input value), the offset is the amount of constant deviation from the set value that remains even when the system enters a steady state, or the amount of that constant deviation. It may also be referred to as a steady-state error or steady-state deviation.

On-Off Control

A control method in which the upper and lower limits of the control range are determined, and control is performed via two positions (start and stop operation, etc.)Also referred to as two-position control.

Operative Temperature

Also referred to as the "Operating Temperature" and is abbreviated as "OT", an indicator of physiological temperature from dry bulb temperature, air velocity, average radiant temperature, and effective body surface area. It is used as a thermal index where the difference between the peripheral wall temperature and the indoor dry bulb temperature is relatively large, such as for radiant heating, etc. When the room airflow is about 0.15 to 0.18 m/s, the curing temperature is regarded as the average value of the dry bulb temperature combined with the average radiation temperature.


PID Control

Also known as proportional integral derivative operation. The control operation generally referred to as PID is one in which an integral operation and derivative, operation are added to a proportional operation. By appropriately setting the proportional band, the integration time, and the differentiation time, stable proportional control without offset can be performed.

Plenum Chamber

A box with a grill for storing and blowing out air whose temperature, humidity, and cleanliness has been adjusted so that it can be blown out to every part of the room. It can be found at the head of an air conditioner, used for relatively small rooms. It may be detachable.

Proportional Action

A control operation in which the operational amplitude on the controller is proportional to the magnitude of the deviation between the input value and the set value. It is also referred to as the P action (for "proportional").A the steady-state error increases when the P value is too small, and cycling occurs when it is too large. The function of manually moving the proportional band by the amount corresponding to the offset (stationary deviation) is called manual reset.

Pump Down

With regard to air conditioning, it is the collection of refrigerant in a refrigerant system into a condenser or liquid receiver performed at the time of relocation or repair of an air conditioning. Also referred to as "Refrigerant Recovery".


Refrigeration Ton

Originally, the ability to convert 1 ton of 0 °C water to 0 °C ice in a 24-hour period was called 1 refrigeration ton, but it may mean the heat flow per unit time. It is also used as a unit for refrigeration capacity, or used as a nominal unit such as when specifying performance ratings. There are also the Japan Refrigeration Ton, JRT, with 1 ton equal to 1000 kg, and the U.S. Refrigeration Ton, USRT, with 1 ton equal to 2000 lb. 1 JRT = 3320 kcal/h = 3861.16 W. 1 USRT = 3024 kcal/h = 3516.85 W.

Relative Humidity

The ratio of the specific weight of humid air to the specific weight of saturated air. It is also the ratio, expressed as a percentage, of the partial pressure of water vapor in humid air, to the partial pressure of moisture in saturated humid air, at the same temperature. The term humidity usually refers to relative humidity.

Resistance Temperature Detector

A temperature sensor which measures changes in temperature as changes in electrical resistance. Materials such as platinum, nickel, copper, and others are used. Measurements may be taken in 3-wire and 4-wire configurations.

Return Air

Return air in the context of air conditioning and ventilation. Return air is divided into reusable air and exhaust.

Return Duct

Also, ventilation duct. A duct that returns air from inside a room that has an air conditioner or ventilation fan. An all-air air conditioning system consists of three parts: a duct, an air conditioner, and a heat source. The duct section is further divided into four types: a supply duct, a return duct, an outside air duct, and an exhaust duct.

Rigid Polyvinyl Chloride Pipe

Pipe manufactured using a polyvinyl chloride resin as a primary material, and generally called polyvinyl chloride pipe or a PVC pipe. These are general-use pipes used for water supply and drainage applications. Usually a thin-walled pipe is used for rainwater applications.


Sensible Heat

Heat that changes the temperature of an object without incuring a phase change.

Sensible Heat Ratio

Sensible Heat Ration = Sensible Heat ÷ Total Heat. Total Heat = Latent Heat + Sensible Heat The ratio of the sensible heat to the latent heat is called the sensible heat ratio, and is required data mainly for determining the airflow of the air conditioner.

Sequence Control

Sequence control is the starting and stopping of equipment or various controls that follows a given procedure. The control of each item is sequentially advanced in a predetermined order.

Servo Mechanism

An automatic control system configured to keep the speed, angle, position, posture, etc. of objects at specified values.


Mud-like sticky scaling that sticks to water-cooled condenser piping.

Sound Absorbing Material

A material used to absorb sound. Soft porous materials such as glass wool, felt, and soft fibers have relatively large sound absorption qualities and there are also materials which absorb resonance such as perforated plates. These materials convert sound energy into other forms of energy to reduce sound reflection, and its performance is represented by the frequency characteristics of sound absorption coefficient.

Star Connection

A method for connecting the secondary side of a three-phase induction motor. A star connection is named that because it is a connection method that connects the starting points of each phase of the three-phase circuit to one place in a star configuration. This connection method can reduce the starting current. General connection methods include the star connection and the delta connection.

Static Pressure

The pressure obtained by subtracting the dynamic pressure of a flowing gas or liquid from the total pressure. It refers to the force per unit area acting in the direction perpendicular to the flow direction, and is expressed in kg/m2 or mmH2O.

Step Response

A stepped response is the response to input signals that suddenly change from one constant value to another constant value.


Cooling of a refrigerant below the condensing temperature under a given pressure. Supercooling also means to cool water below its freezing point of 0 °C. Freezer ice, cooled to –18 °C, is supercooled ice. Supercooling is also called subcooling.

Super Clean Room

A cleanroom with a very high level of cleanliness. A clean room that requires ultra-cleanliness, with no more than one 0.1 particle per ft3.

Super Dry Room

A space that requires an environment with ultra-low humidity. Generally refers to a room where the dew point temperature is controlled to -10 °C or lower.


Surging occurs in the flow rate range where the P-Q characteristic of the fan rises to the right, and the pressure and flow rate become unstable and fluctuate greatly. If operation occurs in this range, vibrations and a surge of air will result so that normal operation cannot be performed due to deformation of the duct, pressure pulsation, and the like.


Thermal Storage Tank

A tank for storing hot water, cold water, or ice as a heating medium.


A thermistor is a semiconductor device whose resistance is highly dependent on temperature such that the resistance decreases as the temperature rises. These devices have a low heat capacity but high sensitivity.


Two types of metal wire are joined, and a pair of conductors are attached which generate a DC voltage (in the mV range) corresponding to temperature. A thermoelectromotive force is generated due to the temperature difference between the reference point and the measurement point, and the temperature is detected by measuring the electromotive force by electrically connecting to the ends of two kinds of metals. Combinations of metals used to form the thermocouple include platinum + platinum-rhodium, chromel + alumel, chromel + constantan, iron + constantan, copper + constantan, and others.

Ton of Refrigeration (U.S.)

One of the units indicating the cooling capacity. In Japan, Japanese refrigeration tons are officially used, but it should be noted that U.S. "tons of refrigeration" may be used with old units before the change to the metric system.1 U.S. ton of refrigeration is 3.024 Kcal/h, or about 10% less than Japanese refrigeration ton.

Total Heat Exchanger

In summer and winter, there is considerable difference between sensible heat and latent heat between the intake air and the exhaust air in a room. For this reason, a device that uses a hygroscopic material is employed in order to exchanges total heat (sensible heat and latent heat) between high-temperature and low-temperature air. The heat exchange rate is generally around 60 to 70%.

Turbulent Flow Cleanroom

This basic type of cleanroom system is widely used in various fields. In this method, dust generated in a room is diffused or diluted with clean air in order to increase cleanliness. The higher the airflow, the higher the cleanliness. However, the turbulence of the airflow limits the cleanliness, and the guaranteed cleanliness limit is about 1000 class. Such systems are often used in conjunction with many clean-systems.・ Cleanliness: Class 1,000-100,000 ・ Ventilation frequency: 15 to 80 times/hour ・ Blow-off air speed: 1 to 2 m/s ・ Positive pressure: 0.5 to 20 mmH2O ・ Construction cost: low ・ Operation cost: low ・ Flexibility: difficult ・ Maintenance: Medium ・ Noise: low → Vertical laminar flow cleanroom → Horizontal laminar flow cleanroom


Ultra Low Penetration Air Filter

An air filter that has a particle capture rate of 99.9995% or more for particles of 0.15 µm at the rated flow rate of the filter. It is an ultra-high-performance filter used in cleanrooms and production equipment that require high cleanliness such as in semiconductor factories, and can remove fine particles of about 0.1 µm, which cannot be removed by HEPA alone. In order to improve efficiency when compared to HEPA filters, the ULPA filter is a product that has a higher filter media density and a thinner filter media to reduce air resistance. Therefore, the disadvantage is that the strength of the ULPA filter is lower than that of the HEPA filter.

Ultrasonic Humidifier

When a rod vibrated by ultrasonic waves is immersed in water, cavitation occurs in the liquid, and a jet-like mist is generated from the water near the surface of the rod. An ultrasonic humidifier is a device that humidifies by supplying these fine water droplets into the air. The water droplets are small, and the device can be installed indoors, but the humidification capacity is small.


Vapor Condensation

The amount of water vapor that can be contained in air is higher as the temperature is higher and lower as the temperature is lower, and if air containing water vapor touches a cold ceiling, floor, wall surface or interior glass surface, piping, ducts, etc., the temperature drops below the dew point of the humid air at that location, causing part of the water vapor to condense into a liquid (water droplet). The case where water droplets are generated on the surface is called surface condensation, and the case where water droplets are generated inside something is called internal condensation.


A design is scientifically based and validatable, and includes verification that it will meet its intended goals.

Variable Air Volume Controller

A device that is installed in the middle of a duct or at a terminal point to limit the amount of air supplied by varying the air flow rate.

Variable Air Volume System

An all-air air conditioning system that varies the amount of air supplied to the air-conditioning target according to the change in indoor heat load.

Ventilation Equipment

Equipment used to keep the air in the target space clean, consisting of exhaust fans, exhaust ducts, hoods and exhaust ports to provide exhaust air in the space, and air supply fans, supply ducts, and supply ports, air filters and the like, in order to provide supply air. The purpose is to secure fresh air (oxygen), and remove dust, toxic gas, and odors.

VOC: Volatile Organic Compounds

Organic compounds that readily evaporate into the air at normal temperatures and pressures, including hydrocarbons such as benzene, toluene, and xylene, and organic chlorine-based compounds such as trichloroethylene and tetrachloroethylene. If volatilized, they becomes air pollutants, and if dissolved in water, can cause soil and groundwater pollution.


Water Hammer

Water hammer refers to an impact force that generates a loud impact sound or vibration that occurs when the fluid flowing through a pipe is suddenly blocked, such as when a pump stops or a valve is suddenly opened and closed. When the flow is suddenly stopped, the velocity energy of the water is instantaneously converted to pressure energy, and the water pressure rises immediately in front of the valve. In an attempt to equalize the pressure of the water in the pipe, this high pressure becomes a pressure wave and reciprocates in the pipeline at a constant and repeating cycle until the pressure returns to the hydrostatic pressure. This pressure wave generates noise and vibration due to the impact when it is reflected at the front of the valve and the pipeline. In order to prevent water hammer, the speed at which the final valve is closed is generally reduced by the force of a spring in order to avoid closing it abruptly.

Water Thermal Storage

A heat storage system that uses water as a heat storage medium. It is the most popular heat storage system for air conditioning. Water has a large heat capacity, is very safe, is easy to handle, and is inexpensive, and at the same time functions as a working medium, and is already being used in heat storage tanks for air conditioning. The biggest difficulty in using water is that its vapor pressure rises rapidly at high temperatures.