Determine optimal flow rate for maximum heat transfer from a solar water heater Determine the efficiency of the solar water heater Develop a predictive model for the solar water heater

1. The Effect of Flow Rate
on Heat Transfer from a
Solar Water Heater
MICHAEL CALFE, KAYLA KERNICH, EMILY SKIBENES

2. What is a Solar Water Heater?
Conversion of sunlight into heat for water
heating using a solar thermal collector
Fuel = Sunlight = Free!
Two Types:
◦ Passive  Passive systems, known as
thermosiphons, circulate water or antifreeze from
the solar collector to the storage tank using the
warm liquid’s natural tendency to rise
◦ Active  Active systems use electric pumps to
increase the efficiency of the water circulation and
to move hot water into the home

3. Importance of Solar Water Heaters
More than 1.5 million homes and businesses currently use solar water heating in the United
States
Assuming that 40 percent of existing homes in the United States have sufficient access to
sunlight, 29 million solar water-heating systems could be installed.
◦ Solar water heaters can operate in any climate.
◦ Performance varies depending on how much solar energy is available at the site, as well as how cold the
water coming into the system is.
Solar water heaters reduce the need for conventional water heating by about two-thirds and pay
for their installation within 4 to 8 years with electricity or natural gas savings.

4. Objectives of the Experiment
Determine optimal flow rate for maximum heat
transfer from a solar water heater
Determine the efficiency of the solar water heater
Develop a predictive model for the solar water
heater

5. Materials:
Solar Water Heater
Peristaltic pump
Bucket of water
Tubing and connectors
Graduated cylinder
Timer
Thermometer
HOBO dataloggers with 3 temp sensors
Hot water, cold water, air

6. Methods:
1) Connect temperature sensors to HOBO; launch
2) Set up solar heater and peristaltic pump (varying flow rates)
3) Measure water flow rate with beaker and timer
4) Place inlet and outlet water temperature sensors;
start HOBO datalogger
5) Operate solar water heater
6) Download temperature data
7) Calculate rate thermal energy gained by heater

7. Steps for Thermal Energy Balance

8. Specifications:
Location:
Clemson, SC Sustainability Shed
Date and time:
4/16/17 2pm-3pm
Dimensions of heater:
19.25 in x 71 in

9. Results: Low flow rate (6.81 mL/s)
Steady State Values:
Ti = 25 deg C
To = 39 deg C

10. Results: Middle flow rate (12.23 mL/s)
Steady State Values:
Ti = 24 deg C
To = 31 deg C

11. Results: High flow rate (21.34 mL/s)
Steady State Values:
Ti = 24 deg C
To = 28.5 deg C

12. Discussion, explain results
Trial # Temp In
(deg C)
Temp out
(deg C)
Flow Rate
(mL/s)
Heat
Transfer (W)
Heat Flux
(W/m^2)
Efficiency
(%)
1 25 39.04 6.81 399.660 453.246 47.44
2 24 31.5 12.23 383.411 434.818 45.51
3 24 28.17 21.34 371.969 421.842 44.15

13. Excel data analysis
370.00
375.00
380.00
385.00
390.00
395.00
400.00
405.00
0.00E+00 5.00E-03 1.00E-02 1.50E-02 2.00E-02 2.50E-02
RateofHeatTransfer[W]
Mass Flow Rate [kg/s]

14. Summarize conclusions
In this experiment, the optimal flow rate for maximum heat transfer was determined to be the
lowest flow rate of 6.81 mL/s

15. Appendix
Equations and actual calculations used.
http://www.eesi.org/papers/view/fact-sheet-solar-water-heating?/solar_water_0506