1. •
Heated Driveway Slab
MEMS 1065
Team Name: Never Slippin’
By:
Matt Hilger
Taylor Koffke
Thomas Reuss
John Claudy
2. Overview
• Background/ Functional
Requirements
• Design of Heat Transfer System
• Fluid Selection
• Thermal Analysis of Piping Network
• Heat Exchanger Design and
Analysis
• Storage Vessel Selection
• Structural Analysis
• Economics
3. Existing Systems
• Electrical
• Huge Yearly Electric Costs
• Hydronic (Like Ours!)
• Almost all installation companies
require boiler supply water to the
heat exchanger (180 F)
• Our system will work with normal
hot water (140 F)
4. Background/Functional
Requirements
• Driveway that is 40’ x 20’
• Must support average large vehicle (25 kN)
• Factor of Safety of 5
• Least expensive method possible
• Piping system must be able to melt snow when temp is 0
degrees Fahrenheit with a wind speed of 10 mph
5. Design of the Heat Transfer
System
• Consists of pipes, a heat exchanger, and a pump
• Process:
• Analyze the pipe network
• Determines flow rate, number of pipes, surface temp. of concrete,
and temp. loss of fluid as it heats up concrete
• Choose heat exchanger
• Recover the temperature loss
• Choose pump
• Based on the pressure drop through piping/heat exchanger
6. Fluid Selection
• Options: Water, Oil, Ethylene glycol,
Propylene glycol
• Water – too high of freezing point,
Oil – high maintenance
• Benefits of EG over PG:
• Low freezing point
• Cheaper
• Better heat transfer qualities – lower
viscosity
•Issues with EG:
• Extremely toxic
• System is in a household w/
possibilities of leaking
•PG is the final choice (40% in aqueous
solution):
• Safer choice and benefit of EG
are not worth the risk
7. Thermal Analysis of Piping
Network
• Serpentine vs. Parallel flow configurations
• Resistance Model
• Convective Flow in pipe
• Conduction through pipe
• Conduction in Concrete
• Ambient Convection
8. Thermal Analysis of Piping
Network
• Accounting for Temperature Changes
• Quantifying Ambient Convection Conditions
• Iterative Process with EES
9. Piping Network Configuration
• Parallel Pipe Configuration Chosen
• Quantifying Number of Pipes Required
• Goals:
• Minimize Pressure Drop
• Maximize Heat Transfer
• Minimize Price, while maintaining Safety
• 27 schedule 40 Pipes with diameter of ¾”
11. Heat Exchanger Analysis
Bell & Gosset
BP412 model brazed plate heat
exchanger
Hot Water Flow
Rate (gpm)
Number of Plates Height (mm)
8.0 60 240
TPG,
out(℃)
Twater,
out(℃)
U
(W/m2*K)
LMTD
(℃)
q (Btu/hr)
40.8 28.3 2542 11.0 ~227,000
12. Tankless Hot Water Heater
• Can increase 8.4 gpm
water temperature by 45
degrees F to 140 F
• Traditional water heater
will heat to 95 F and the
tankless heater will do
the rest of the work
• Fueled by Natural Gas
13. Pump Analysis and Design
• Total Head loss through the pipe
system: 42.7 ft.
• Required Horsepower: 0.15
• Operation point of 13.5 gallons/min and
42.7 ft of head
• Cole Parmer Centrifugal Pump
• Type H (Model # 70761-02)
14. Storage Vessel Selection
• Requirements:
• Can withstand the pressure of Propylene Glycol (~65 psig)
• Has a small capacity (~5 gallons)
Capacity Diameter Overall Height J L H
5 gallons 10” 19” ¾” ½” 1”
18. Structural Analysis of Slab
• All dimensions for the slab were determined by past experience or thermal analysis
• Thickness was determined by experience
• Hole size, spacing, and distance from top by analysis
24. Economics
• Assumptions: (4% interest rate,
$11,000 loan, 3 years)
• Salvage value= 20% of IC of
System
• Present Worth ~ $38,000
25. Conclusion
• Successful Design of Driveway Heating system to maintain 40 degree Fahrenheit
Surface Temperature in varying ambient conditions
• Successfully pairs with a standard hot water heater
• Utilizes safe materials for heat transfer
• Does not affect the strength of the driveway
• Contains safeguards against damage to the system such as pressure and temperature
gauges
• Competitive System with current driveway heater designs
• Increases value to the Property
• Does NOT require a boiler for operation
