Transcript Humidification in Healthcare Facilities

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HUMIDIFICATION
Presentation
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Introduction to Humidification
Why Humidity is so Important
Why Should We Humidify
Typical Applications
Calculation Parameters
Existing Local Variables
Hardness of Water
Types of humidifiers
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Isothermal / Adiabatic
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Isothermal
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Electric Humidifier
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Gas-Fired Humidifier
Steam to Steam Humidifier
Direct Steam Injection Humidifier
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Resistive
Electrode
Multi-Steam Distribution
Jacketed Tube Distribution
Adiabatic
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Atomizing Humidifier
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Air/Water Fogger
High pressure Water
Ultrasonic Humidifier
Evaporative Humidifier
Humidity: Water that is in gaseous form, vapour.
Relative humidity (% RH): The amount of vapour in air at a specific temperature with
respect to the maximum quantity of steam that can absorb without condensation.
Humidification: This process occurs when the water has absorbed enough heat to
evaporate. It requires about 1,000 Btu to evaporate one pound of water (2.326 kJ / kg).
70% of the planet is covered by water.
The human body is composed of roughly 60% water by volume.
The gaseous form of water is vapor and the measure of water vapor in the air we
breathe is relative humidity.
The amount of vapor the air can hold is dependent upon the temperature of the
air. The warmer the air the more vapor it can hold. The reverse is true for cooler
air.
We function best at temperatures between 70 and 80 degrees and relative
humidity of 40% to 60%.
If the air is dry and hot we lose body water by evaporation very quickly and thus
our skin and sinuses are dry and we are always in need of replenishing the lost
water.
Indoor environments in the winter are generally very dry in northern countries
and so there is a need to add vapor so that we feel and function better.
All land based animals have similar problems with the relative humidity around them.
In fact just about all material both living and inanimate is affected by the amount of
vapor in the air.
Paint, plastics, silicone, paper, textiles etc.; Many manufacturing processes require
close humidity and temperature control in order to maintain product quality.
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Indoor air quality (Health, Comfort and Productivity)
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Material protection and storage
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museums, archives, libraries, wood/paper, textiles, food processing
Environments for specific processes
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schools, health care facilities, offices, living space
Printing, clean rooms, pharmaceuticals, laboratories, semiconductors
Animal rooms/research, Zoological facilities
Static electricity
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computer rooms, data processing areas, hazardous environments, munitions,
aerospace, paint spray booths
2008 ASHRAE, HVAC Systems & Equipment, Chapter 21
By E.M. Sterling, A. Arundel, and T.D. Sterling, Ph.D.
Museums / Libraries
35-50%RH
Offices / Hotels / Schools
35-40% RH
Clean rooms / Data Centers
Pharmaceuticals / Labs
35-60% RH
40-50% RH
Hospitals / Health Care
Printing Industry
Tobacco Industry
35-50% RH
40-50% RH
60-70% RH
 Design Conditions
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Outside temperature/RH(%) and desired indoor conditions
 Load calculation (lbs/hr) for ventilation system
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Natural: Space/Room Size/Number of air changes
Mechanical: Total Air Flow and % of outside air
Economizer: Total Air Flow and Mixed Air Temperature
 Distribution
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Airflow direction, AHU/Duct size and Absorption Distance
Self contained
• Supply water quality
– City or well, softened, reverse osmosis or de-ionized
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Energy source
– Electricity, natural or LP gas, boiler steam or chemical-free boiler steam, High
temperature hot water, Evaporative/atomizing
OTHER PARAMETERS TO CONSIDER
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Initial investment
Energy cost comparison
Space available
Steam distribution configurations
Maintenance requirements
Vapor barriers
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Description: Water is considered a universal solvent. In drinking water there are
several minerals that are dissolved.
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Hardness is determined by the concentration of calcium and magnesium
dissolved in water (ppm). Montreal city water 116ppm
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Precipitate: When water evaporates, the minerals create deposits.
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Water Treatment: water softeners, reverse osmosis or de-ionized systems
Isothermal
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Electric Humidifier
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Adiabatic:
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Resistive
Electrode
Gas-Fired Humidifier
Steam to Steam Humidifier
Direct Steam Injection Humidifier
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Multi-Steam Distribution
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Jacketed Tube Distribution
Atomizing Humidifier
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Air/Water Fogger
High pressure Water
Ultrasonic Humidifier
Evaporative Humidifier
Isothermal
Humidifiers
Pros
Cons
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Clean sterile steam
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Cost of energy
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Compact size
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Creates a certain cooling load
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Low installed cost
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Limited capacity
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Close humidity control
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If electric generation is close, very efficient
Resistive type
Pros
Electrode type
Pros
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Permanent cleanable chamber
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Works in all water qualities
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Output can be held very close
Cons
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Required tank cleaning can be
difficult
Bottle change out is easy and fast
Cons
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Replacement bottles are expensive
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Complicated control system wastes too much water
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Capacity loss as electrodes becomes coated, unit will stop
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Water quality affects operation and operating cost
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Bottles are not enviromentally friendly
Pros
Cons
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Clean sterile steam
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Large foot print
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Large capacity available
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Low energy cost
Installation requirements (flue
/combustion air)
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Close control
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Creates a cooling load
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80-85% efficient
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Must have gas supply
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Not good for small loads
Pros
Cons
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Clean sterile steam
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Must have a central steam supply
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Large capacity
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Large foot print
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Closes boiler loop
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Creates a cooling load
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Can be difficult to maintain
Pros
Cons
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Large capacity
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Must have a central steam supply
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Low initial installation cost
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Home run steam / condensate
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Close control
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Chemical carry over / dirty
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Open loop for boiler
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Must keep the steam jacket hot
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Creates a cooling load
Configurations
Multi-Steam Distribution
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Consists of vertical tubes connected
to a header
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Short non-wetting distance
Jacketed Tube Steam Distribution
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Jacket preheats the steam distributor tubes
Horizontal distributor installation only
Steam nozzles facing the airstream
Adiabatic
Humidifiers
Adding moisture to air can be accomplished with no
addition of energy from external source. The air
evaporates the water by itself, using a part of its
sensible heat to accomplish the task, cooling the air
as it absorbs moisture.
Isothermal
Humidification
Adiabatic
Humidification
As the air absorb moisture and moves up the wet
bulb line, the RH and the air temperature are both
changing, but the total heat content (enthalpy)
remains unchanged.
This natural phenomenon is used to save energy
costs by augmenting mechanical refrigeration in
warm, arid climates. Buildings are cooled and
humidified simultaneously using this principle. It is
also used in cold climate when humidification is
needed in buildings that have surplus internal heat
from equipment or electronic gear.
Pros
Cons
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Evaporative cooling
Small droplet size
Very large capacity
Can be put directly in space
Long nozzle life
Low maintenance
Fully modulating
Requires high inlet temp
Long absorption distance
Wetting of duct/standing water
Potential for bacteria growth
Particulate deposits/dust
Pure water preferred
Air compressor cost/kWh cost
Pros
• No air compressor
Cons
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Large droplet size
Very long absorption distance
Short nozzle life
High maintenance
On/Off or staged control only
Pros
• Compact size
• Small water droplet size
Cons
• High initial cost
• Must have ultrapure water supply
Pros
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Very low power consumption
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Potable or pure water
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Low initial cost
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Cleanable, low maintenance
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No standing water in duct
Cons
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Duct pressure drop
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On/Off or staged control
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Not good for close
humidity control