IRC Research and Technology Forum VFD’s For Evaporators

IRC Research and Technology Forum

VFD’s For Evaporators

Ian Runsey Guntner U.S. LLC

1


Agenda;

� Introduction

� Analysis Of VFD Concept For Evaporators

� Additional Considerations When Using VFD’s

� EC Technology As An Alternative

� Conclusions

2


Introduction;

� Why Use VFD’s On Evaporators

� What Are The Pros

� What Are The Cons

� Does it make sense to use VFD’s on Evaporators

3


Why Use VFD’s On Evaporators;

• Energy Savings

• Temperature Reached

• Reduced Load / Partial Loads

• Seasonal Operation (esp. Northern Regions)

• Sound Levels

4


What Are the Benefits of Using VFD’s On Evaporators;

• Energy Savings – NO Wasted Energy

• Reduced Electrical Costs (kWh)

• System Efficiency

• Not Only the Fans / Motors but elsewhere in the System

• Added Value to End Users / Owners

• Lower Sound Levels

5


What Are the Negatives of Using VFD’s On Evaporators;

• Reduced Air Throw

• Air Throw is Proportionate to Impeller Speed / Frequency

• Uneven Temperature Distribution

• Product Deterioration / Damage / Loss

• Reduced Capacity of Coil

• Motor Resonance

6


However;

• Reduced Air Throw, &

• Uneven Temperature Distribution……

• …… Can be Accounted for by Ramping Up Drive Periodically

• Dependant on Facility Layout, and

• Every Facility Will Be Different

7


8

Power Input Considerations When Utilizing VFD’s;

What Does It Cost To Run Your Facility?? (kWh)


3

1

212

∗=

n

nPP

P1 = power consumption motor - 100 %

P2 = power consumption motor – reduced operation

n1 = speed – 100 %

n2 = speed - reduced operation

Fan Speed Air Volume Power Sound (dB)

benchmark

100.00% 100.00% 100.00% 0

95.00% 95.00% 86.00% -1.1

90.00% 90.00% 73.00% -2.3

70.00% 70.00% 34.00% -7.7

50.00% 50.00% 13.00% -15

25.00% 25.00% 1.60% -30

9


10


11


12


13

power Pel. 4 fans 100%3.3kW x 4 = 13.2kW


ON

ON ON

ON

ON ON

ON ON

n = 100 %Pel. = 100 %

n = 100 %

Pel. = 100 %

n = 100 %

Pel. = 100 %

n = 100 %

Pel. = 100 %

n = 100 %

Pel. = 100 %

n = 100 %

Pel. = 100 %n = 100 %

Pel. = 100 %

n = 100 %

Pel. = 100 %

Power Pel. per fan = 3.3kW

Power Pel. all fans = 13.2 kW

Evaporator Running at 100% Air Q

4 x 36” Fan Evaporator, 5HP Motors (45TR ~ 73,000cfm)

On / Off Control Variable Frequency


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power Pel. 4 fans 13%0.43 kW x 4 = 1.72kW

ON

ON

n = 100 %Pel. = 100 %

n = 100 %

Pel. = 100 %

n = 50 %

Pel. = 13 %

n = 50 %

Pel. = 13 %

n = 50 %

Pel. = 13 %

n = 50 %

Pel. = 13 %n = 0 %

Pel. = 0 %

n = 0 %

Pel. = 0 %

Power Pel. per fan = 3.3kW

Power Pel. all fans = 13.2 kW

Evaporator Running at 50% Air Q

4 x 36” Fan Evaporator, 5HP Motors (45TR ~ 73,000cfm)

On / Off Control Variable Frequency

OFF

OFF

3

1

212

∗=

n

nPP

ON ON

ONON

375%


15

I

n

r

u

s

h

F

L

A

F

L

A

AC Inrush Current 3.5 X FLA

With On / Off Operation

Current Ramps up to FLA

With VFD


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When Not To Use A VFD On An Evaporator;

• DX Coil With Thermal Expansion Valve…

• … Electronic Expansion Valve Can Be Acceptable

• ***) ASRS Facilities Can Be Designed Differently…

• …With Initial Low Air Flows – Thermal Effects

• OR, any other Facilities with Low Traffic Patterns

***) Recommendation


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810 ft

111 ftStacking

Height

108 ft

Unit Coolers

Downblow

39.5°F

42 °F (Design)

44.6 °F

Temperatures

side view

Air velocity

top view

Air flow pattern

side view


18

Additional Considerations with VFD’s for Evaporators;

• Ensure a Clean Coil (NO Frost)

• Reduced Frost = Lower Airside PD…….

• …Maintains Coil’s Rated Capacity

• …Results in higher CFM and Air Throw

• …Lower Power Input for same CFM


19

Additional Considerations with VFD’s for Evaporators

• Venturi geometry Optimum for Impeller

• Minimum Impeller Tip Clearance

• Optimized Impeller Geometry (Efficiency)

• Leading Edge of Impeller within Venturi

• Overall Efficiency levels Maximized


20

0

50

100

150

200

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

airflow volume / Volumenstrom [m³/h]

sta

tic

pre

ss

ure

/ s

tati

sc

he

r D

ru

ck

[P

a]

FE050-4D_.4I.6, KD + BS FE050-4D_.4I.6, VD resistance curve

15 % more airflow using full

bell mouth!

Full bell mouth

Short bell mouth



• Use of Long Throw Adapters / Air Streamers

• Could be Beneficial at Lower Frequencies (Air Throw)

• Streamer Does not Constitute an Air Side Pressure Drop

• Long Throw Adapter Incurs additional ESP

21


22

Air flow speed

Axial distance (air throw)

Without

streamer

With

streamer

** Thermal short-

circuiting **



• Choice of Fin Pattern – Parallel or Staggered

• Fin Spacing / Variable Fin

• Rate of Frost Formation

• Increase in Evaporating Temperature (Lower TD)

• Higher COP – System Efficiency [1K (1.8°F) = 3%]

• Not Only For VFD’s – but will result in better performance

23


EC – Motor Technology;

• As an alternate to VFD – AC Inverter Duty Motors

• Electronically Commutated Motor

• Permanent Magnet Brushless DC Motor

• Standard AC Motor is an Induction Motor

24


25

Integrated ElectronicsMotor Protection

Temperature Control

Alarm Relay

Soft Start

Speed Control

EC MotorRotor with Permanent Magnet


VFD and 3~ Induction Motor;

• Squirrel Cage Rotor

• Slip Losses in the Rotor

• Motor Temperature Rise

• Filtering of VFD Output is Critical

• Cables & Harmonics

• Distance From Drive

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Brushless DC Motor (EC);

• Permanent Magnets in Rotor

• No Slip Losses

• Precise Motor Speed Control

• Exact Feedback from Motor

• Matched System of Drive &

Motor

• Highest Motor Efficiency at all

Frequencies


EC – Motor Technology;

• Electronic Controls Completely Integrated

• Overload Protection Incorporated

• 4 – 20mA, 0 – 10V Control Input; 0 – 10V Linear Output

• Always has Correct Rotation

• Excellent Acoustics / Harmonics (Wiring & Cables)

• NO Contactors

• Lower Installed Cost

• Reliability and Lower Life Cycle Maintenance Costs

27


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Conclusion;

• VFD’s Are A Viable Option For Evaporators

• Significant Energy Savings Can Be Realized At The Evaporator

• Additional Impact On Overall System Efficiency

• Ensure Best Defrost Practices ……

• …… Huge Energy Savings Can Be Realized

• Air Side Efficiency Should Be Maximized

• EC Motors Are An Alternate To VFD’s

• Life Cycle Costs vs. Initial Costs Is The End Users Right To Know


29

Questions???

Thank You For Your Attention

Ian Runsey

Guntner U.S. LLC

1870 N. Roselle Rd.

Schaumburg, IL

60195

Documents

IRC Research and Technology Forum VFD’s For Evaporators