Consideraciones éticas

Fan and pump systems share many similar characteristics and as a consequence may be analysed in similar ways from an energy perspective. Each is typically driven by a motor, either directly or through a belt or gearbox. Both systems will frequently utilize centrifugal devices to create motion in the fluid or air, and as a result both systems are governed by a set of rules, known as affinity laws. The affinity laws describe the relationship between speed, flow, pressure and power required:

Q_{2 ı} N₂ P_{2 ı}

∙

∙

∙

∙

N = speed, Q = flow, P = pressure, kW = kilowatt

The power required for movement of air or fluid in the system downstream of the fan or pump is governed by the pressure drop presented by the system to the flow. Both systems share significant losses in friction downstream and consequently share similar opportunities for flow balancing, static and dynamic head (pressure) reduction, and speed control rather than throttling for flow control.

Identifying energy savings opportunities in fan and pump systems involves critically assessing the existing energy use. Table 2.10 provides examples of EMOs for fan and pump systems according to the three-step method detailed in Section B-8, “Identify Energy Management Opportunities.”

The various losses shown in the Sankey diagram in Figure 2.5 are itemized and defined in Table 2.9. A similar diagram for a pumping system is provided in Section B-8, “Identify Energy Management Opportunities.”

Figure 2.5 Sankey Diagram of Fan System Energy Flows

Distribution Meter Motor _Fan Damper Duct Drive Energy In Energy Out Only 20% Filter Total Losses = 80%

Component _EfficiencyTypical

Meter 100% Distribution 96% Motor 85% Drive 98% Fan 60% Damper 70% Filter 75% Ductwork 80% Overall 20% = = =

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Energy Flow description key Factors for Evaluation _{of Flow} Portable instrumentation _{used for Evaluation}

Electric Distribution Systems Losses

Heat from resistance of the

wires Voltage drop in wiring

Handheld power meter or clip-on ammeter

Motor Losses

Heat created at the motor in conversion from electric to mechanical power

Motor efficiency rating and operating conditions, i.e. applied voltage, loading and temperature

Motor efficiency rating, temperature measurement of motor, tachometer to check motor loading from speed Drive Losses

Heat created due to friction in the bearings pulleys and belts and bearings

Belt tension, bearing and belt

temperature Infrared temperature measurement

Fan (Pump) Losses

Heat created due to friction and fluid viscous losses with the fan (pump)

Fan (pump) efficiency rating at operating point defined by flow rate and pressure as specified by the fan (pump) curve

Flow and pressure measurement

Damper (Valve) Losses

Heat and pressure drop created by friction damper (valve)

Damper (valve) setting and pressure

drop inlet to outlet Differential pressure measurement

Filter (Strainer) Losses

Heat and pressure drop created by friction to airflow in filter (strainer)

Pressure drop across filters (strainers) Differential pressure measurement

Ductwork (Pipework) Losses

Heat and pressure drop created by friction within ductwork (pipework) to air (water) flow

Pressure drop per unit length or

overall Differential pressure measurement

Air (Water) Power Delivered

The amount of air (water) power delivered at the terminal point such as the diffuser or outlet (end-use heat exchanger)

Pressure difference and flow achieved

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step actions d et er m in e th e n ee

d q Determine the requirement for air/water flow, possibly in terms of a profile over time.

q Determine the range of pressures that the fan/pump will need to overcome. q Determine if the need for flow is fixed or variable.

q Determine the duration of the need for flow (hours per day).

M at ch th e n ee d

q Provide and use manual control of fans/pumps.

q Control operating times of fans/pumps by automatic control. q Conduct an air/water balance with qualified contractors. q Eliminate or reduce throttling as a means of flow control.

q For fan systems with a fixed flow requirement, reduce flow rates to the requirement by: q reducing fan speeds by sheave changes

q shutting down extra (backup) fans

q For pump systems with a fixed flow requirement, reduce flow rates to the requirement by:

q changing or trimming pump impellers q shutting down extra (backup) fans

q For fan or pump systems with a variable flow requirement, vary flow by: q using a two-speed motor

q using a variable speed drive

q Eliminate leaks in the ductwork and pipework.

M ax im iz e Effi ci en cy

q Provide proper maintenance for fans and pumps: q Lubrication

q Belts and pulleys

q Pump and fan overhaul and cleaning

q Reduce pressure drops or pipework/ductwork resistance by: q cleaning interior of pipes/ducts

q maintaining filters/strainers

q using efficient ductwork/pipework practices q Select and install a more efficient pump or fan:

q More appropriate design for the application q New equipment/technology

q Install a more efficient motor.

o pt im iz e su pp ly

q Consider the use of small steam turbines, typically in place of pressure reducing valves, to drive large fans and pumps (i.e. boiler feedwater pump, boiler forced draft or induced fan).

q Consider the use of an alternative such as diesel engines with heat recovery to electric motors as prime movers.

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Energy-Efficient Motor Systems Assessment Guide, Natural Resources Canada, 2004

oee.rncan.gc.ca/cipec/ieep/newscentre/motor_system/index.cfm

CanMOST: The Canadian Motor Selection Tool, Natural Resources Canada, 2004

oee.nrcan.gc.ca/industrial/equipment/software/intro.cfm?attr=24

Variable Frequency Drive (VFD) video, Natural Resources Canada, 2005

oee.nrcan.gc.ca/industrial/equipment/vfd/vfd-video.cfm

Industrial Energy Efficient Equipment, Natural Resources Canada

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