Www.clima2005.ch Optimized HVAC for the 21 st Century Donald R. Wulfinghoff, P.E. Wulfinghoff Energy Services, Inc. Wheaton, Maryland USA 301 – 946 – 1196.
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Clima 2005 Lausanne | Solothurnstrasse 13 | CH-3322 Schönbühl | Switzerland
8th REHVA World Congress | Phone +41 (31) 852 13 00 | Fax +41 (31) 852 13 01 | Email: info@clima2005.ch
www.clima2005.ch
Optimized HVAC for the 21st Century
Donald R. Wulfinghoff, P.E.Wulfinghoff Energy Services, Inc.
Wheaton, Maryland USA
301 – 946 – 1196 DW@EnergyBooks.comwww.EnergyBooks.com
A REVOLUTION IN 45 MINUTES
Contemporary HVAC equipment and design practices are obsolete. They cannot satisfy the stringent requirements of the 21st Century for:
The essential changes can be made quickly.
Here is how to do it.
ENERGY EFFICIENCY
HEALTH
RESISTANCE TO TERRORISM
THE LOGIC
1. HVAC systems are either multiple-zone or single-zone.
2. Multiple-zone air handling systems inherently cannot perform all HVAC functions and operate efficiently. So, they must be abandoned.
3. Single-zone systems can satisfy all HVAC functions efficiently.
4. But, contemporary single-zone HVAC equipment performs poorly because of flaws in design and equipment.
5. We will solve the design problem by introducing a new approach to design that optimizes every function required by the application.
6. We will solve the equipment problem by showing how to correct all the flaws of contemporary single-zone equipment.
Multiple-Zone Air Handling SystemsInherently Cannot Satisfy All HVAC Functions
1. Temperature control of individual spaces forces a 3‑way compromise between COMFORT, VENTILATION, and ENERGY EFFICIENCY.
2. All multiple-zone systems inherently have: INEFFICIENT and/or INADEQUATE VENTILATION HEALTH HAZARDS FIRE HAZARD AIR TRANSPORT LOSSES AIR LEAKAGE into Idle Spaces and Equipment And Now, … VULNERABILITY TO TERRORISM
These deficiencies of multiple-zone air handling systems are INHERENT.
They cannot be fixed.
So, multiple-zone systems must be ABANDONED.
Footnote: VAV is a Failed Experiment
Ventilation is radically worse than with constant-volume systems.
Improving comfort and ventilation requires a return to reheat.
Discomfort is endemic. Combining heating and cooling is problematic.
An Interesting Trend: Fan-powered VAV terminals are an evolution toward single-zone systems.
So, …the optimized HVAC of the 21st century will use SINGLE-ZONE systems exclusively.
They can avoid all conflicts between energy efficiency and the HVAC functions.
They can avoid all health hazards.
They cover smaller areas, limiting the spread of fire and noxious agents.
Then, WHY are SINGLE-ZONE Systems Not the Primary Choice for HVAC Today?
DESIGN DEFICIENCIES: Designers neglect to tailor single-zone systems to the functions needed by the application. (Multiple-zone systems tend to be multi-functional, although inefficient.)
EQUIPMENT DEFICIENCIES: Lack of rational humidity control Ineffective control of ventilation Failure to exploit opportunities for efficiency Generally poor quality
INTRODUCING
OPTIMIZED-FUNCTION DESIGN
IMPROVING DESIGN PRACTICE
OPTIMIZED-FUNCTION DESIGN
addresses every function
of each application
in an optimum manner.
The Steps of OPTIMIZED-FUNCTION HVAC Design
1. Define all the HVAC functions that are needed for each application in the facility.
2. Define the spatial zones that correspond to each function. (Zones may differ for different functions.)
3. For each zone, select equipment to fulfill each function optimally.
4. Consolidate the equipment.
5. Optimize the control of the equipment.
The Steps of OPTIMIZED-FUNCTION HVAC Design
1. Define all the HVAC functions that are needed for each application in the facility.
2. Define the spatial zones that correspond to each function. (Zones may differ for different functions.)
3. For each zone, select equipment to fulfill each function optimally.
4. Consolidate the equipment.
5. Optimize the control of the equipment.
The Common Functions of HVAC(More Than You Realize!)
FUNCTIONS NOT INVOLVING O.A. FUNCTIONS INVOLVING O.A.
Raise Space Temperature Select Cleanest Outside Air
Lower Space Temperature Use Outside Air for Cooling
Raise Space Humidity Raise Humidity of Outside Air
Lower Space Humidity Lower Humidity of Outside Air
Distribute Conditioned Air Control Pressure Relative to Outside
Circulate Air for Comfort Remove Outside Air Pollutants
Remove Space Air Pollutants Recover Sensible Heat from Exhaust
Control Pressure Between Spaces Recover Latent Heat from Exhaust
Limit Spread of Fire Prevent Intake of Noxious Agents
Limit Spread of Noxious Agents
… AND perform all these functions with minimum energy!
The Steps of OPTIMIZED-FUNCTION HVAC Design
1. Define all the HVAC functions that are needed for each application in the facility.
2. Define the spatial zones that correspond to each function. (Zones may differ for different functions.)
3. For each zone, select equipment to fulfill each function optimally.
4. Consolidate the equipment.
5. Optimize the control of the equipment.
The Steps of OPTIMIZED-FUNCTION HVAC Design
1. Define all the HVAC functions that are needed for each application in the facility.
2. Define the spatial zones that correspond to each function. (Zones may differ for different functions.)
3. For each zone, select equipment to fulfill each function optimally.
4. Consolidate the equipment.
5. Optimize the control of the equipment.
The Steps of OPTIMIZED-FUNCTION HVAC Design
1. Define all the HVAC functions that are needed for each application in the facility.
2. Define the spatial zones that correspond to each function. (Zones may differ for different functions.)
3. For each zone, select equipment to fulfill each function optimally.
4. Consolidate the equipment.5. Optimize the control of the equipment.
EQUIPMENT CONSOLIDATION(One Unit is Needed for Each Zone)
(Filters, humidifiers, and controls are omitted for clarity.)
Fulfilling all the functions of the application usually does NOT require a potpourri of equipment.
A high degree of EQUIPMENT CONSOLIDATIONis possible.
A high degree of STANDARDIZATION is possible.
The Steps of OPTIMIZED-FUNCTION HVAC Design
1. Define all the HVAC functions that are needed for each application in the facility.
2. Define the spatial zones that correspond to each function. (Zones may differ for different functions.)
3. For each zone, select equipment to fulfill each function optimally.
4. Consolidate the equipment.
5. Optimize the control of the equipment.
Conditioning Mode F1 F2 C1 C2 H D1 D2 D3 D4 D5 D6 D7 D8
Heating: all conditions O O X X O O O X O X O X O
Mechanical cooling: no dehumidification needed
O O O X X X O O O X O X O
Mechanical cooling: low outside humidity, inside moisture requires dehumidification
O O O X O X X X O X O X O
Mechanical cooling: outside humidity requires dehumidification
O O O O O X X X O O X X O
Economizer cooling: mechanical cooling not needed
O X X X X O X O X X X O O
Economizer cooling: supplemental mechanical cooling required, but not dehumidification
O X O X X X O O X X X O O
Economizer cooling: supplemental mechanical cooling and dehumidification
O X O X O X X X X X X O O
Purge Cycle (for cooling or air cleaning) O X X X X O X O X X X O O
Zone Shutdown X X X X X X X X X X X X X
Legend: F – Fan. All fans are variable-speed. C – Cooling coil H – Heating coil D – Damper. All dampers are 2-position (fully open or fully closed) R – Heat recovery (coil or heat exchanger) A – Air flow sensor O – “on” (for fans and coils) or “open” (for dampers) X – “off” (for fans and coils) or “closed” (for dampers)
Provide OPTIMUM CONTROL for ALL Conditions
ECONOMICS
of Optimized-Function HVAC
COST ISSUE(in order of cost)
PERFORMANCE (Relative to Multiple-Zone Systems)
Human Productivity & Health Major Improvement
Energy Cost Much Lower
Loss of Rentable Space Much Less
Equipment Cost About Same
Insurance Against Hazards Much Less Expensive
Maintenance More Expensive, but Minor
FIXING THE EQUIPMENT
OPTIMIZING
DEHUMIDIFICATIONIN SINGLE-ZONE SYSTEMS
ABOLISH
“CHEAP MOTEL SYNDROME”
24 C, 40%
11 C, 100%
DRY BULB TEMPERATURE (F)
80
40
40
6050
50
60
70
70
80 90 100 120
90
.004
.016
.012
.008
.028
.024
.020
32 C, 90%
The Solution is REHEAT
24 C, 40%
11 C, 100%
32 C, 90%
DRY BULB TEMPERATURE (F)
80
40
40
6050
50
60
70
70
80 90 100 120
90
.004
.016
.012
.008
.028
.024
.020
Isn’t Reheat EXPENSIVE?Not in single-zone systems. It’s FREE.
Reheat is expensive in multiple-zone systems because it is used for temperature control in addition to humidity control.
But, single-zone systems do not need reheat for space temperature control.
A cooling system always rejects enough heat to provide free reheat for humidity control.
REHEAT for humidity control in single-zone systems is FREE
because it can be done entirely with REJECTED HEAT
1. Heat rejected in any cooling process always exceeds the cooling load.
2. Reheat needed for dehumidification is always less than the cooling load.
3. Single-zone systems do not need reheat for other functions (temperature control).
Reheating with condenser heat is the most efficient method of dehumidification by cooling that is possible:
It INCREASES THE EFFICIENCY of the cooling equipment.
It is even more efficient than using “renewable” energy sources for reheat.
REHEAT in a HYDRONIC Conditioning Unit
Reheat coils must be enhanced to exploit the LOW TEMPERATURE of rejected heat (typically ca. 50 C), which is further reduced by hydronic heat transfer.
Condenser cooling water has low energy density, so it is important to MINIMIZE HEAT LOSS and PUMPING ENERGY. Otherwise, pumping energy will add significant cost to dehumidification.
DESIGN CHALLENGES WHEN USING REJECTED HEAT
IN HYDRONIC SYSTEMS
OTHER DEHUMIDIFICATION IMPROVEMENTS(not explicitly single-zone issues)
Dehumidify where moisture concentration is greatest. Include latent heat recovery. Eliminate moisture retention on cooling coils.
OTHER DEHUMIDIFICATION IMPROVEMENTS(not explicitly single-zone issues)
Dehumidify where moisture concentration is greatest. Include latent heat recovery. Eliminate moisture retention on cooling coils.
OTHER DEHUMIDIFICATION IMPROVEMENTS(not explicitly single-zone issues)
Dehumidify where moisture concentration is greatest. Include latent heat recovery. Eliminate moisture retention on cooling coils.
FIXING THE EQUIPMENT
OPTIMIZING
VENTILATIONIN SINGLE-ZONE SYSTEMS
NOTORIOUS VENTILATION DEFECTSIN SINGLE-ZONE SYSTEMS
Inability to regulate outside air intake accurately.
Air infiltration into spaces and equipment during idle periods.
ACCURATE CONTROL OF OUTSIDE AIR ABOLISH CONTROL DAMPERS! This requires 2 steps:
1) Control ventilation air intake with variable-speed fans.
2) Control fans with air flow monitoring.
PREVENTION OF OUTSIDE AIR LEAKAGE
Install HERMETIC dampers for ISOLATION.
OTHER SINGLE-ZONE VENTILATION IMPROVEMENTS
Optimize outside air economizer cycle. Incorporate exhaust air heat recovery.
OTHER SINGLE-ZONE VENTILATION IMPROVEMENTS
Optimize outside air economizer cycle. Incorporate exhaust air heat recovery.
IMPROVE VENTILATION SYSTEM DESIGNOUTSIDE THE EQUIPMENT BOXES
(not explicitly single-zone issues)
Cleanest air Isolated from wind pressure Inaccessible to mischief Warmest or coolest air source,
depending on requirement
Improve the efficiency of air distribution to the occupants.
Control ventilation rate in response to need.
Select the best air intake source.
THE FINAL
REFINEMENTSIN OPTIMIZED-FUNCTION SYSTEMS
MINIMIZE AIR MOVEMENT ENERGY
ELIMINATE ALL HEALTH HAZARDS
MINIMIZE AIR MOVEMENT ENERGY Abolish control dampers (another reason). Bypass idle coils.
MINIMIZE AIR MOVEMENT ENERGY Abolish control dampers (another reason). Bypass idle coils.
ELIMINATE ALL HEALTH HAZARDS Sterilize air handling equipment continuously. Include appropriate filtering, biocides, etc.
to eliminate hazards from the air stream.
ELIMINATE ALL HEALTH HAZARDS Sterilize air handling equipment continuously. Include appropriate filtering, biocides, etc.
to eliminate hazards from the air stream.
EQUIPMENT MANUFACTURING ISSUES
Optimized HVAC equipment is easy to manufacture, not significantly more difficult than contemporary equipment.
Existing equipment serves as prototypes for optimized equipment.
Much existing equipment can be used in optimized systems as it presently exists.
ONWARD TO THE FUTURE!
Design Your HVAC for this Century, Not the Last One
The Survival of Civilization Depends on It
Let the discussion continue:
Donald R. Wulfinghoff, P.E.Wulfinghoff Energy Services, Inc.
Wheaton, Maryland USA
301 – 946 – 1196 DW@EnergyBooks.comwww.EnergyBooks.com
In LAUSANNE: Tulip Inn
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