Temperature Humidity and Ventilation Flashcards
Define heat?
Heat is a form of energy (the ability to do work); the random vibration of molecules of the body. Adding heat to a substance increases its molecular motion and potential energy, and may cause it to undergo a change of state that is to melt or vaporize.
Define the effect that heat has on air volume and air density?
Volume increases as air gets warmer
density decreases as air gets warmer
What happens to a substances molecular structure when heat is added?
Adding heat to a substance increases its molecular motion and potential energy, and may cause it to undergo a change of state that is to melt or vaporize.
What is conduction?
The transfer of heat through a substance.
What is convection?
The transfer of heat by natural motion of a fluid medium.
What is radiation?
The transfer of heat by energy waves, similar to light waves and radio waves.
What is a BTU relative to water?
1 BTU is the amount of heat required to raise 1 pound of water 1 degree Fahrenheit.
What is a BTU relative to air?
1 BTU is the amount of heat required to raise 55/ft³ of air 1 degree Fahrenheit.
What direction does heat travel?
Heat travels from warm to cold.
What is sensible heat?
The heat required to change temperature in a substance, but not a change of state.
What is latent heat?
The amount of heat required to change the state of a substance without changing its temperature.
What is specific heat?
It is the number of BTU’s required to raise the temperature of 1 pound of a substance by 1 degree Fahrenheit.
How is sensible heat measured?
By a thermostat or by sense of touch.
How is latent heat measured?
BTUs
What is humidity?
The quantity of water in a particular volume of air.
What is relative humidity?
A measure of the amount of water air holds at a certain temperature. it is relative compared to the amount of water that air, at that same temperature, can hold at 100% humidity or saturation.
What is saturated air?
When air contains the maximum amount of vapour possible for a particular temperature, the air is said to be saturated.
What is dew point temperature?
The temperature that moisture will start to condense from the air.
True or false: Hot air is denser than cold air.
False.
What instruments are used to measure humidity?
Hygrometer and psychrometer
What are the effects of low humidity on people?
Static electricity, dry throat, nose bleeds and dry skin. Having too little humidity in the air will also make you feel cooler. This is caused by the moisture in your skin evaporating which uses heat energy from your body.
What are the effects of low humidity on furniture?
Too little humidity can affect the building and objects in side as well. As humidity level drops moisture content in objects such as wood paper textiles also give up their moisture. This will cause wood to shrink and crack, paper will dry out and start to crumble.
What is the function of a humidistat?
A humidistat controls the humidifier, turning it on or off as required.
What are methods for reducing humidity in a home?
Removing moisture absorbing shower curtains, installing proper ventilation in bathrooms bringing cold fresh air into the duct system and by the use of dehumidifiers.
What are the requirements for fresh air in a new residential construction?
Each room must have 5 L/s or 10 cfm of air coming into it except for the master bedroom and undeveloped basements which must have to 10 L/s or 20 cfm.
How does an HRV work?
And HRV pre-heats incoming fresh air by forcing it through a heat exchanger core with a fan. At the same time another fan is forcing warm exhaust air through the other side of the core allowing heat to transfer from warm exhaust air to the cooler fresh air without letting the two flows come in contact with each other.
True or false: In order for a temperature difference to occur, a latent heat change must take place.
False.
True or false: Hygrometers can be used to show direct readings of relative humidity?
True.
On a psychometric chart, where is the dry bulb temperature scale?
Along the bottom.
On a psychometric chart, where is the wet bulb temperature scale, and what shares it?
Top arching line, shared with dew point scale.
On a psychometric chart, what is the arching line running central of the chart?
Relative humidity line.
On a psychometric chart, what lines run vertically?
Dry bulb temperature lines.
