• Condenser Fan Research

The purpose of this study is to develop an air conditioner condenser fan that reduces the electric energy use of the outside condensing unit.  To accomplish this, researchers are designing and producing more aerodynamic fan blades and substituting smaller horsepower (HP) motors which achieve the same air flow rates as the larger, less efficient motors typically used.

To create baseline data, a test condensing unit (Trane 2TTR2036) was installed and a benchmark test completed.  Measurements were made of the condenser airflow, motor power, sound levels, and condenser cabinet pressures. Test results favorably compared with the manufacturer's test data. Afterwards, an experimental set of fan blades ("A") designed for a 1/15 hp motor at 1650 rpm was numerically created and then successfully produced using rapid prototyping.  These prototype blades were substituted on the original condenser, and all test measurements were redone.   Design-A was found to reduce power by 25% (50 watts) with approximately equivalent airflow to the original condensing system. A second prototype 19" fan ("B") was produced and tested, designed for the higher condenser cabinet pressures researchers had observed.  This combination performed even better than design-A with a 62 watt reduction (32%) over the baseline condensing unit.

Testing in Year 5 will include additional testing of design-B and the design, fabrication, and testing of a larger, four-bladed, 27.6" fan design. 

• Fenestration Research

American Society of Heating, Refrigerating, and Air Conditioning Engineers (ASHRAE) Technical Committee:  In 2002, BAIHP researchers wrote a statement of work for the development of a methodology to calculate solar spectral distributions incident on windows for various sun positions and atmospheric conditions.  ASHRAE approved the project and sent it out for bid. Completion of this work project should make it much easier to determine the true solar heat gain through spectrally selective fenestration systems for varying atmospheric conditions and solar altitude angles.

Calorimetric Measurements of Complex Fenestration Systems:  FSECs research calorimeter will be used both indoors with the FSEC Vortek solar simulator and outside under natural solar radiation, on its Sagebrush solar tracker, for window solar heat gain experiments.  The results of this testing will offer a way to test the solar gain properties of complex and other non-standard fenestration options for industrialized housing, such as exterior and interior shades and shutters, and those placed between the panes of double pane windows.

• Sagebrush Solar Tracker:  The computer program running the calorimeter, the Sagebrush tracker, and both together is complete.  It contains a user-friendly graphic interface and offers a wide variety of experimental opportunities.  There are many channels for adding additional temperature sensors and the calorimeter/tracker can be operated with either the sun as a source - in a variety of tracking modes - or with FSECs Vortek solar simulator.

  To conduct outdoor testing, the Neslab chiller must be connected to the flow meter, the temperature sensors to the calorimeter, and the calorimeter mounted on the tracker.  The Sagebrush tracker now is functional, responding properly to commands sent from the computer, rotating in altitude, and azimuth and stopping when the limit switches are encountered.  A telescopic sight and level for positioning it outdoors in the proper orientation for accurate solar tracking has been designed and is near fabrication completion.

Figure 61.  Side view of calorimeter before it was mounted on the Sagebrush Tracker

The Neslab chiller and remote controller have been connected to a Gateway laptop computer and a RS-485 serial interface card necessary to operate the calorimeter has been installed.  Researchers can now send commands and receive data from the chiller.  Although the calorimeter is designed to work directly with the existing FSEC hydronic loop used for testing solar collectors, the Neslab will give an independent, standalone capability to the calorimeter.  (Please see Figure 61, above.)

The water flow meter purchased for measuring the flow into the calorimeter has been  successfully connected to the Agilent (HP) 34970A data acquisition system and its measurements were incorporated into the calorimeter operating program.  Temperature sensors also successfully connected to the data acquisition system, are reading properly, and have been incorporated into the calorimeter program.  The program has coding to include a number of additional temperature channels once the temperature probes have been received and installed in the calorimeter.  Another 20-channel input card is being purchased for the Agilent, to permit additional temperature readings. Knowing the flow rate and temperature difference, the heat delivered to the water by the calorimeter can now be accurately determined.

Now that all portions of the system are operational, researchers will configure the outdoor system, verify, and begin testing in Year 5.

Vortek Solar Simulator: In 2003, the Vortek Simulator was fired up and operated reliably on the calorimeter testing with FSEC's solar collector test apparatus.  As expected, a few computer and other problems delayed initial data collection by a couple of days.  However, these problems were corrected and testing proceeded normally.

During testing, the calorimeter was connected to the existing facility's hydronic loop, which was developed over a period of years to a temperature stability of 0.01 degrees centigrade.  The irradiance level measured about 820 watts per square meter over an aperture of 0.557 square meters.  The calorimeter was tested as though it were a flat plate collector, to obtain its efficiency curve.  This was used to infer the thermal losses and solar heat gain coefficient of the eighth inch clear single pane of glass used for the test.  The nominal wind speed was set by the laminar blower to five miles per hour.  The coolant flow was run at levels of 0.2, 0.5, and 1.0 gallons per minute (GPM), and at varying inlet temperatures.

For all test runs, steady state conditions were established by observing the outlet temperature in a real-time plot as equilibrium was approached.  During periods of non-equilibrium, the recorded data was used to measure the first-order system time constant, a function of the flow rate.  The calorimeter time constant varied from 1.5 minutes at 1.0 GPM to 6.9 minutes at 0.2 GPM.  These time constants were obtained by blocking the incident beam and watching the decay in outlet temperature.  

Skylight Dome Transmittance:  Researchers completed work on the skylight dome transmittance, adding a spherical shape to the cylindrical one previously used.  The ray tracing programming was changed to eliminate reflection of rays approaching the dome from the inside, for comparison with the analytical model, which does not yet include internal reflections.  The difference between the two calculational approaches, at a 30E solar zenith angle is 1.7%, considered acceptable for rating skylight performance.

With both cylindrical and spherical dome models, transmittance at large solar zenith angles above 60 is substantially greater than for a horizontal flat plate.  This is because most of the rays incident on the dome and entering the skylight are incident on the dome close to perpendicular, where dome transmittance is highest.

Energy Gauge USA and Energy Gauge FlaRes: BAIHP mapped a table of window and shade characteristic simulations that could be run with these two programs.  These runs will be used to determine the energy use of various fenestration options for Florida residences and to guide the preparation of instructional materials.

Florida Market Transformation: From the beginning of the BAIHP program, researchers have  provided technical background information and support to the Alliance to Save Energy and the Efficient Windows Collaborative to promote the sale and installation of energy efficient fenestration in hot climates (such as Florida) and other areas for both conventional and industrialized homes.  BAIHP also provides advice, technical information, and educational information to energy companies regarding window energy performance, and answers technical and general inquiries by phone, email, and the Internet.

National Fenestration Rating Council (NFRC) Technical Committee: In 2002, BAIHP presented a final report at a Task Group meeting in Houston, on the NFRC- funded work to develop a draft standard practice for the rating of tubular daylighting devices.  That project is now complete.

In 2001, BAIHP researchers performed a number of ray traces on a highly reflective cylinder of varying lengths, using the trace results to determine the cylinder's transmittances for different interior surface reflectivities (from 90% to 100%).  These results generated a  "default table" for determining the transmittance of this tubular daylighting component.  Using simplified assumptions, then multiplying the tube transmittance by the top and bottom dome transmittance results, researchers determined the total transmittance for a chosen sun angle.  Based on the findings, BAIHP provided NFRC and the industry with a list of suggested research projects to test and develop this methodology further. One of these submitted project's was sent out for bid by ASHRAE in Year 4 and is expected to begin in Year 5. 

Tubular Daylighting Device SHGC and VT Value Calculations:   Following a request from the TDD industry, a sequence of operations and a new computer program were written to access the Window 5 glazing database and obtain from it the spectral transmittance and front and back reflectance data for any sheet of glazing in that database which might be used in making the top dome of a tubular daylighting device.  This permits determination of the input parameters needed to run TDDTrans.

The computer program was posted for free download and is available by clicking on http://fsec.ucf.edu/download/br/fenestration/software/TddTrans-Beta/TDDTrans.exe. 

Access sequence:

• Download and run the Optics 5 program.
• Select the glazing to be used in the tubular daylighting device.
• Export its spectral data file as a standard ASCII text file.
• Specify this file in an input window of the new program OptPropConvert.exe along with the glazing thickness corresponding to the Optics 5 spectral data file.
• OptPropConvert then calculates from this, the solar-weighted and photopic-weighted. material refractive index and solar-weighted and photopic-weighted material absorptivity.

These four numbers will be entered into the TDDTrans.exe program, a new thickness specified for the dome material, and the program will calculate the average solar-weighted and photopically-weighted transmittance of the top dome, the reflective cylindrical tube, and the bottom diffuser, based on additional user inputs.