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Senior Design Team #18Senior Design Team #18
Lacey EdnoffLacey EdnoffBrianna BeconovichBrianna Beconovich
Jarimy PassmoreJarimy PassmoreJesse PoormanJesse Poorman
Presentation Overview Objective
Product Specifications
Design Concept
Component Analysis Theoretical & Experimental
Cost Analysis
Conclusion 3D Drawings & Bill of Materials
Future Plans
2
Objective Use the waste heat from a window AC unit to heat water in a 40 gallon tank
Heat the water initially from 70°F to 120°F in under 3 hours
Utilize customers existing 40 gal hot water heater
Working fluid is R-22
Assemble for less than $500
Commercially available parts
Easy installation & reproducible
3
External Heat Exchanger
CPVC piping
Coaxial Coil
System utilizes force convectionRequires a pumpMay need insulation
4
Douchette Model CX-H075
Pump
Component Analysis
Blue: Already performed, Red: To be performed prior to final presentation
5
Component Analysis Performed
AC Window Unit Minimum amount of heat required for system
External Heat Exchanger Analytical overall heat transfer coefficient, Experimentally measure mass flow rate, inlet and outlet Temperature & Pressure
Internal Heat Exchanger Analytical overall heat transfer coefficient, Experimentally measure mass flow rate, Inlet and outlet Temperature & Pressure
Piping & Fittings
Volumetric Flow rate, Velocity, Pressure Drop and Total Head
Pump System Curve for pump power
Table 1: System components to be analyzed
Selection of AC Window Unit Assumptions:
Hot water heater is well insulated i.e. no heat loss to surroundings All of the heat is transferred to the water
∆T : Temperature change equal to 50 °F
Cp : Specific Heat of Water
mh2o : Mass of water
ΔTCmQ poh 2
6
Total amount of heat transfer required to heat the water: Q = 16,667 BTUIn order to heat the water in 3 hours:
Final selection: Frigidaire Model Qdot = 8000 BTU/hr
7
Heat Transfer Assumptions The system is steady state
Closed system i.e. Heat loss from fluid 1 = heat gain by fluid 2
Thermal properties of the materials are constant
Air properties are constant and evaluated at the appropriate Temperatures
Resistance to heat flow within the copper tubing is negligible, so the temperature is uniform throughout
Goal is to determine if the chosen heat exchanger is sized correctly to efficiently transfer the heat from the R-22 fluid to the water
8
Heat Exchanger AnalysisRate of Heat transfer is governed by the overall Heat transfer coefficient, U
Compared the air-cooled system to the modified water-cooled systemMeasured Surface Temperatures of the AC unit System
Temp before and after condenser ( T
H
i
n
& T
H
o
u
t
) T
emp of ambient air and air after condenser( T
C
i
n
& T
C
o
u
t
)
For the Doucette CX-H075 Coaxial Coil Heat exchanger:Used manufactures operating Temperatures
Qdot UA LMTD( )
TH in
TC out
TH out
TC in
Fluid 1 (warm)
Fluid 2 (cold)
9
Volumetric Flow Rate for Water
TC
QV
pavg
Determined Volumetric Flow rate as function of ΔT Assumed a constant heat transfer rate Defined ΔT across the heat exchanger in increments of 5 deg
Piping Layout Divided into 3 sections due to difference
in in diameters of pump, heat exchanger, and hot water tank inlets
Section 1: Hot water heater to Heat exchanger ½” Schedule 40 CPVC
5 90 deg elbows
1 Ball valve
1”- ½” Reduction
Section 2: Heat Exchanger ½” - 5/8” Expansion
5/8”- 3/4” Expansion
Section 3: Heat exchanger back to Hot water tank ¾” Schedule 40 CPVC
4 90 deg elbows
10
1
3
2
11
Pressure drop across the piping
g
VK
D
fLz
g
V
g
Pz
g
V
g
PH
h 222
2
1
2
112
2
22
Assumptions:
For each section of piping Velocity remained constant
Modified Bernoulli Equation
The major and minor losses associated with each section of the piping were calculate individually to find the total pressure drop as a function of change in temperature
Used manufacture specifications for the pressure drop across the heat exchanger
This lead to the calculation of the total hydrostatic head which helped in determining an appropriate pump
12
Hydrostatic Head as a function of Ball Valve Position
0
2
4
6
8
10
12
14
16
18
0 1 2 3 4
Volumetric Flow (gpm)
Hea
d (
ft) System (a = 60 deg)
System (a = 50 deg)
System (a = 0 deg)
By changing the angle of the ball valve position, the head can be increased
Hydrostatic Head vs. Volumetric Flow
Pump Selection
Operatingpoint
RequiredPressure
Head
DesiredFlowRate
Pump curve was approximated from manufacture specsSelection based on cost and low volumetric flow rate
p/g
V
13
Cost AnalysisExternal Heat Exchanger Cost Analysis
Total Cost $421.46
$44.33 $8.98
$41.95
$97.20$169.00
$60.00 Fittings
Piping
Pump
Heat Exchanger
A/C Unit
R-22
14
Conclusion
1 External Heat Exchanger2 ¾” CPVC elbow3 ½” CPVC elbow4 AC Unit5 Hot water heater6 Ball Valve7 ½” CPVC Pipe8 ½” Connector9 ¾” Connector10 1/2”-5/8”Compression Fitting 11 ¾”-5/8” Compression Fitting
15
Gnatt Chart
16
Future Plans Analysis of the internal heat exchanger design
Overall heat transfer coefficient, Inlet and Outlet Temperature of R-22
Length of tubing required
Mounting
Pump, A/C Unit
Thermostat
Assembly
Experimental Analysis of working Fluid R-22
Pressure, Temperature, Mass flow rate
Heat exchanger effectiveness, System efficiency
17
References
Oak Ridge National Laboratory
http://www.ornl.gov/
Doucett Industries
http://www.doucettindustries.com
Janna, William. Design of Fluid Thermal Systems 2nd Edition. PWS Publishing Company 1998
18
Special Thanks!!
Dr. Steve Van Sciver
Dr. Chang Shih