Heating Cost for 5000 Gallons of Water at 100 o T $32.80 85% 90% 80% $30.87$29.15 Thermal Efficiency...
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Transcript of Heating Cost for 5000 Gallons of Water at 100 o T $32.80 85% 90% 80% $30.87$29.15 Thermal Efficiency...
Heating Cost for 5000 Gallons of Water at 100o T
$32.80
85%
90%
80%
$30.87$29.15
Thermal Efficiency
Daily Operating Costs @ $0.63/Therm
“What Happens to Water When Heated”
Heated water becomes more corrosive...
More electrically conductive...
Expels dissolved gases...
Precipitates dissolved solids
85% of water in USA contains dissolved minerals
Hardness - Calcium & Magnesium (grains/gallon)
Total Dissolved Solids - All other minerals (mgl or ppm)
Pounds of Lime Deposited vs.... Temperature and Water Usage
0
30
60
90
120
150
180
210
0 300 900 1500 2100 2700 3300 3900WATER USAGE IN GALLONS PER DAY
PO
UN
DS
OF
LIM
E D
EP
OS
ITE
D
PE
R Y
EA
R
180oF
170oF
160oF
150oF
140oF
120oF
Tank-Type Water Heaters
Extremely Susceptible to Scale -
Minimal Velocity
Thin construction
Low Thermal Efficiency
Short life
Scale Accumulation vs. Efficiency
Te
mp
era
ture
of
flu
e g
as
Distance
Fireside
Waterside
Heat Transfer Surface
Scale buildup
without scale
with scale
Operating Costs of a Commercial Water Heater
$$
1/4”3/8”
1/2”
38%
5/8”
48%
60%
74%
Source: Engineered Systems May/June 1988
Efficiency Loss % Scale Accumulation
in Inches
The Energy Robber!
Original Price vs. Long Term Cost
Decrease inThermalEfficiency
5%
10%
7.5%
6% 9.3% 12.8%
Increase in Fuel Cost for Life of Product
How to Control Scale The rate of scaling increases with temperature and usage.
In water tube-type equipment, this can be offset by increasing the water flow over the heat transfer surfaces, as this reduces the tube surface temperatures.
The turbulence of the flow, if high enough, works to keep scale that does precipitate off the surface.
Water Heating Equipment Design Goals
Make the Heating Surface Self Cleaning
Allow Room for Scale and Sediment to Fall Out
Incorporate a Means to Clean out Sediment
Lower the Heat Flux Rates
Circulating Tank Concept(Separate Water Heater and Tank)
Flexibility in Equipment Selection
Equipment Longevity
Continued Efficiency
Component Serviceability
Ease of Installation
Ease of Maintenance
High Efficiency Circulating Tank Water Heater
ScrubbingAction
Copper-fin UnitCopper-fin UnitStorageStorage
TankTank
ContinuousContinuousPumpPump
Copper-Fin Heat Exchanger
Near Perfect Heat Transfer Surface
Thermal Conductivity Higher Than Steel/Cast Iron
More Surface Area
Corrosion Resistant
Proven Heat Exchanger Design
Copper Heat Exchanger Principle
Controlled velocity scouring action Constant temperature monitoring Impervious to thermal shock Low water content Low standby loss
Heat Exchanger Construction
ASME Code Section IV 160# working pressure, 240# test
pressure “O” Ring and Gasketless construction Straight tube, 7/8” inside diameter,
balanced flow
“Straight-Tube” vs. “Coil-Type”
Maintenance
Deliming Kits and Tees
Pressure Drop
Serviceability
Continued Efficiency
Continued Efficiency
85% 85% 85% 85%85%
41%
50%
63%
78%
67%
0%
20%
40%
60%
80%
100%
START-UP 1 YEAR 2 YEARS 3 YEARS 5 YEARS
TH
ER
MA
L E
FF
ICIE
NC
Y
SCRUBBING NON-SCRUBBING
EFFECTS OF SCALING ON EFFICIENCYEFFECTS OF SCALING ON EFFICIENCY
Energy Savings
Benefits of Scrubbing vs Non-Scrubbing Water Heater Design
Equipment Longevity
Ease of Maintenance
Continued Efficiency
What vent options are available?
Conventional - Category I Side-Wall - Category III & IV Direct Vent Sealed Combustion - Category
I, III, & IV Outdoor