Characteristics of waterBoiling point – 212F @ sea level, higher altitudes?
Freezing point - 32F
Specific heat – 1.0 Ammonia has highest
ice and steam SH = .5
Specific weight 1.0
Latent heat of fusion – 144 BTU/lb.
Latent heat of vaporization – 970 BTU/lb.
PH – 7 neutral – (less is acid more is base)
Mpemba (IM PEM BAH)effect
Altitude affects boiling point
Altitude (ft) Altitude (m) Pressure (mm-Hg) Temp. °F Temp. °C
0 0 759.85 212.0 100.0500 152.4 746.54 211.1 99.50
1000 304.8 733.46 210.2 99.011500 457.2 720.60 209.3 98.522000 609.6 707.98 208.5 98.032500 762.0 695.57 207.6 97.543000 914.4 683.38 206.7 97.053500 1067 671.41 205.8 96.574000 1219 659.65 204.9 96.084500 1372 648.09 204.1 95.605000 1524 636.73 203.2 95.12
Specific weight of water = 1.0Aluminum 2.7
Copper 8.96
Iron 7.87
Lead 11.3
Brass 8.4
Magnesium 1.74
Zinc 7.14
Lead 11.3
Water 1.00
Ice 0.917
Specific weight of oils = .8 -.95
Temperature- t -(oF)
Density
- ρ -(slugs/ft3)
Specific Weight
- γ -(lb/ft3) (lb/gallon)
32 1.940 62.42 8.343640 1.940 62.43 8.345150 1.940 62.41 8.343060 1.938 62.37 8.337870 1.936 62.30 8.329080 1.934 62.22 8.317690 1.931 62.11 8.3077100 1.927 62 8.2877120 1.918 61.71 8.2498140 1.908 61.38 8.2048160 1.896 61 8.1537180 1.883 60.58 8.0969200 1.869 60.12 8.0351212 1.860 59.83 7.9957
Specific heat
Specific heat of water = 1
Material (cal/g °C) (J/kg K) (cal/g) (J/kg)
Aluminum 0.215 900 94.5 3.96x105
Copper 0.092 385 49.0 2.05x105
Iron 0.107 448 63.7 2.67x105
Lead 0.031 130 5.5 0.23x105
Brass 0.092 385 Unknown Unknown
Magnesium 0.245 1030 88.0 3.7x105
Zinc 0.093 390 27.0 1.1x105
Styrofoam 0.27 1131 Unknown Unknown
Air 0.240 1006 N/A N/A
Water 1.000 4190 N/A N/A
Ice 0.500 2095
BTU’s required to heat water
It takes 1 BTU to heat 1 pound of water 1 degree F
BTU’s = pounds X temp. diff.
Latent heat of fusion
Pounds x 144 BTU’s
Latent heat of vaporization
Pounds x 970 BTU’s
Heat 200 pounds of ice @ 20F tosteam @ 220F.
PH factor
Pure water = 7 (neutral)
Above 7 – alkaline, tends to scale
Below 6 – acidic, tends to corrode
Maintaining temperature below 160Ftends to inhibit scaling in an opensystem. A close system generally willnot scale at higher temperatures.
Mpemba effectDiscovered in 1969 by student in Tanzania, Africa
Hot water freezes before cold waterWHY?
1. Good conduction – no frost2. Convection currents more active and reduced
insulating ice.3. Evaporative effect4. Warm water has less gaseous impurities
GAMA
Gas Appliance Manufacturers Association
http://www.gamanet.org/
Operating cost
Step 1. BTU’s = Lbs X TD
Step 2 Fuel = BTU’sBTU per unit X EF
BTU’s per unit
Oil- 144,000 per gallon
Natural gas – 100,000 per therm or 100 cubic feet
LP gas – 94,000 per gallon
Electric – 3413 per KW
Water mixing formulas
What will temperature be if 60 gals @ 120 degrees are mixedwith 30 gals @ 60 degree
Temp = (Q1 X Temp1) + (Q2 x Temp2)/ (Temp2 + Temp1)
= (60 X 120F) + (30 X 60F) / (120F + 60F)
= (7200 + 1800) / 180
= 9000/180
= 112.5F
Water mixing formula 2
If the cold water is 60F and there is 40 gals of 140F wateravailable, how many gals can be produced @ 95F
Q1 = Q2 x TD tankTD desired
= 40 gals. X (140F-60F)95F – 60F
= 40 gals. X 80F35F
= 320035
= 91.4 gallons
What happens when we lower the temperature to 120F?
Recovery Rate
Burner capacity X efficiency
8.33 x temp. rise
Recovery RateA 40,000 BTUH WH, 80% efficient, is capable
of supplying ________ gallons per hour atan 80F temperature rise.
1. Determine net output
40,000 BTUH x .80 = 32,000 BTUH
2. Determine amount BTU’s needed to raiseone gallon 80F
8.33 X 80 = 666.4
3. Recovery rate = 32,000666.4
= 48 gals per hour
First hour rating
First hour rating = recovery rate + tank capacity
= 48 gals. + 40 gal. tank
= 88 gals.
Affect of GPM on temp rise
Temp. Rise = BTUH (output)GPM X 500
500 = 8.33lbs. X 60 min.
Converting metric to imperial
Gallons = liters3.79
Liters = gallons X 3.79
Converting Fahrenheit to Celsiusand VS
F = (9/5 X C) + 32
C = 5/9 X (F – 32)
9’
40’
30’
Calculating volume
Volume of square or rectangular shaped building = area X height, or length X
Volume = length X width x height= 30’ X 40’ X 9’= 10,800 cubic feet
Volume of a triangular building = area of triangle X length or height
50’
6’
24’
Step 1. Area of triangle = length X height2
= 24’ X 6’2
= 72 sq. ft.
Step 2. Volume of triangle = area X length= 72 sq. ft. X 50’= 3600 cubic feet
Volume of a cylinder = Area of circle X length of cylinder
10’
30’
Step 1. Area of circle = π X Radius2 or πR2
= 3.14 X (5’ X 5’)= 3.14 X 25 square feet= 78.5 square feet
Step 2. Volume of cylinder = area of circle X length of cylinder= 78.5 square feet X 30’= 2355 cubic feet
Gallons = cubic feet / 7.48
Weight = cubic feet X 62.3 lbs.or
= gallons X 8.33 lbs.
Selecting a water heater
Conventional Storage Water Heaters
Demand (Tankless or Instantaneous) WaterHeaters
Heat Pump Water Heaters
Solar Water Heaters
Tankless Coil and Indirect Water Heaters
Conventional Storage Water Heaters
Demand (Tankless or Instantaneous)Water Heaters
Heat Pump Water Heaters
Solar Water Heaters
Tankless Coil and Indirect Water Heaters
Metlund or Chilipepper system
Heat traps
FVIRFlammable vapor ignition resistance
•A device to prevent ignited vapors frompassing out of the combustion chamber
•A one way intake system to control themovement of makeup air into thecombustion chamber
•An inner door and burner assembly tocreate a sealed junction with thecombustion chamber, preventingcombustion air and flammable vaporsfrom entering the chamber through thefront of the water heater
FVIR- TroubleshootingFlammable vapor ignition resistance
1. The installation environment may be dirty.
2. Temperature conditions exceed the TCO switchcutoff limit. Temperatures exceed 115° F
3. The water heater may be starved for combustionair. Don’t forget an electric dryer, it also consumes air.
4. There may not be a draft at the water heater drafthood.
5. A flammable vapor incident has occurred.
N.C. Plumbing Code Chapter 5
Section 501- water heater must be set at 120F. If thewater heater is used for space heating it may be set above120F. If the temperature is above 140F a mastertempering valve must be installed. (ASSE 1017).
Customer may set temperature above 120F but no oneelse may
Section 502.5
Water heater source of ignition must be 18” abovegarage floor. Both fossil fuel and electric.
Exception: FVIR appliances
Mechanical Code Section 1002.2
Water heaters used for space heating must beapproved for such use.
Note: When replacing a water heater used forheating be sure to replace with same BTUHrating.
Gas pipe sizing
Natural gas
LP gas
Venting – single appliance
How house pressurization affectsgas flame
Tax credits for solar WH
Federal - 30% until 2016 – no limit
North Carolina – 35% - $1400 limit
Solar water heating
Solar constant =429.2 BTU’s per sq. ft.
170 – 300 Btuh’ per sq. ft. reach the earth
Three types of solar energy to be collected
Direct – 300 Btu/sq. ft.
Diffuse – 50 Btu/sq. ft.
Reflected – 60 Btu/sq. ft.
Insolation
Average KWH/sq. meter/ year
Collector orientation
Face TRUE south (15 degree variation)
Tilt angle = degree latitude - water heating only
Degree latitude plus 15 degrees - space heating
(10 degree variation acceptable)
Flat plate collector
Glazing selection
High shortwave transmittnace (.2 – 3.0 micrometers)
Low longwave transmitance (greater than 3.0micrometers)
Low absorbance at all wavelenghts
Excellent weatherabilty
Single vs Double Glazing
For water heating only single glazing is all that’sneeded in our area.
Areas of low insolation would benefit with doubleglazing
Absorber Plate
Black Paint
97% absorbtion
97% emisstivity
Selective Surface
95% absorbtion
9-12% emisstivity
vs
Collector sizing
20 square feet per person for first two
8 square feet each person thereafter (sun belt)
12-14 square foot per person(north)
Corrosion Control
Prevent direct connection of anodic and cathodicmetals or supply sacrificial anodes.
Corroded end (anodic)
Magnesium
Zinc
Aluminum
Carbon steel
Brass
Tin
Copper
Bronze
Stainless steel
Protected end(cathodic)
Storage tank sizing
1.5 gallons per square foot collector area.
2 gallons per square foot in very sunny areas
These rules of thumb will prevent overheating
Transfer FluidsWater
+ cheap, high heat content, safe
– freezes, suports galvanic corrosion, boils at lowtemperature, promotes scale formation
Water/Glycol
+ will not freeze above –35F, can handle corrosioninhibitors
- Must be replaced regularly, not stable at hightemperatures, boils slightly above water
Hydrocarbons
+ Low cost, no freezing problems, nontoxic
- breakdown at high temperatures (become acidic), thickenwhen cold causing pump overload.
Silicon Fluids
+ do not freeze, do not boil, do not corrode, will last LOS
- Initial cost
Controls
Pump sizingCollector loop
Determine the head +adjusted friction losses
Determine the GPM
water- GPM = sq.ft. collector X .015
Silicon - GPM = sq. ft. collector X .039
Storage loop
Use manufactures specs
