Current Research

Measurements of Office Equipment Heat Gain Data, 1742-TRP (Sponsor: ASHRAE)

Office equipment heat gain data in the current ASHRAE handbook was last updated in 2009. Since then, office equipment has evolved dramatically, from simple operating modes to a more complex functions.

Today’s computer power consumption depends on actual computing load rather than merely on the stated full clock speed. Additionally, solid state technology and power saving modes have decreased computer power consumption during typical use. Preliminary data showed that power consumption for an up to date tablet PC varies between only 3 and 20 watts, while a desktop PC’s that uses the same technology consumes between 2.5 and 109 watts. The strong dependency of power consumption on equipment usage therefore requires to change from a default value (current ASHRAE tables) towards equipment and usage type dependent weekly load profiles.

This project will conduct an in-depth field study, analyze the resulting data, and update the ASHRAE fundamentals chapter 18 tables 8-12 from outdated equipment using diversity factors to weekly load profiles of up to date equipment. This update will allow design engineers to obtain load estimates that are more accurate, allowing to properly select equipment. On the research and building controls optimization side, the load profiles will allow to optimize new control algorithms for realistic load cases without needing to take costly detailed measurements.

 

Advancement of DOE's EnergyPlus Building Energy Simulation Program (Sponsor: DOE-FSEC)

Oklahoma State University works as a member of the development team on the EnergyPlus building simulation program.  Detailed information about EnergyPlus can be found on www.energyplus.gov. OSU works to assist users of the program as well as enhancing simulation capabilities, and developing/implementing/testing new models based mostly around primary plant simulation and equipment.  Project duration: April 2006 - Present

 

Design and construction of a new psychrometric research test facility at Oklahoma State University (Sponsor: AAON Inc.)

The low temperature psychrometric chamber artificially reproduces the temperature and relative humidity of various climates around the world, from tropical to continental, from dry desert to northern and polar tundra. The temperature can range from -40 to +130°F (-40 to 55°C) and the relative humidity from 10 to 95% R.H.

 

 

This psychrometric chamber is used to experimentally study the behavior of systems and components under specific ambient conditions. Primarily intended for testing heat pumps, refrigeration systems, and unitary equipment up to 20 tons (70 kW) of refrigerating capacity, the facility consists of two similar-size adjacent rooms of about 19 by 20 by 18 feet high. The large floor area can accommodate multiple set ups inside each room. A double panel sliding door (shown in figure here) is located next to a gantry crane, which is used to position the testing equipment inside the chamber. Project Duration: May 2007 - Present

 

Foundation Heat Exchanger Model and Design Tool- Development and Validation(Sponsor: ORNL/DOE)

Can very energy efficient houses be heated and cooled by a ground-source heat pump with ground heat exchangers placed only in the foundation excavation?  Though this has been experimentally successful in a few test houses, the combination of house design, weather conditions and ground properties that allow such a low-cost ground heat exchanger design are unknown.  The goal of this project is to develop design procedures, simulation methodologies and software that facilitate design of such systems.  For cases where the ground heat exchanger solely in the foundation excavation is not sufficient, we are also looking at additional heat sinks/sources that can be used as part of a residential hybrid ground-source heat pump system.

This figure shows preliminary results from a simulation of a ground heat exchanger with six HDPE tubes. The left-hand side of the plot is the foundation wall; the top of the plot is the ground surface. Project Duration: September 2008 - Present

 

Methodology to Measure Thermal Performance of Pipe Insulation at Below-Ambient Temperatures (Sponsor: ASHRAE)

Insulation systems applied to cold piping for refrigeration and de-humidification systems aim to prevent water vapor condensation on the pipe exterior surface. When a chilled fluid pipe is inadequately insulated, such condensation might occur and water drip onto the building surfaces possibly causing mold growth. In addition, moisture ingress into piping and tubing insulation can lead to degrading service life and performance of the insulation systems, corrosion of pipelines, and mold growth on the surface of the insulation.

In this project, the low temperature psychrometric chamber at Oklahoma State University is used to demonstrate a new test methodology for measuring the effective thermal conductivity of pipe insulation systems when these systems are exposed to dry and wet ambient conditions similar to the ones of field service in chilled water, refrigeration, and liquefied gas transport applications. The outcomes are used for updating the information regarding mechanical system insulation design and for building a new experimental apparatus for pipe insulation product testing. project duration: August 2008 - Present

 

Waterside Fouling Performance of Brazed-Plate Type Condensers in Cooling Tower Applications (Sponsor: ASHRAE)

The water fouling test facility is designed to experimentally measure the heat transfer rate and hydraulic performance of plate heat exchangers (PHEs) under fouling conditions. The current set up replicates similar operating conditions as in the actual field of service. A variable-speed pump circulates refrigerant inside the testing PHEs. Refrigerant condenses at the ARI conditions of 105 to 110°F Saturated Condensing Temperature, 85°F Entering Water Temperature, and water flow of 3.0 GPM/ton. The overall heating capacity is up to 37,000 Btu/hr (11 kW).

The water fouling facility is currently used to determine the fouling resistance of water cooled brazed PHEs by using simulated cooling tower water. The simulated cooling tower water is prepared in a batch inside the conical tank shown in the figure. Water is then pumped through a series of pipelines into the plate heat exchangers and it is possible to develop correlations of fouling resistance and pressure drop with the water quality. Project duration: May 2008 - Present

 

Microchannel Coils in Compact Heat Pump Systems (Sponsor: OCAST)

This project focuses on the development of a new microchannel heat exchanger that can be used as the outdoor coil in compact heat pump systems for residential and commercial applications. The work, sponsored by the Oklahoma Center for Advancement of Science and Technology (OCAST), aims to advance the technology of microchannel heat exchangers and address the main challenges that arise when these heat exchangers are used as outdoor evaporator coils in R22 and R410A systems. Both modeling and experimental efforts will provide the basic research required to address three significant problems related to the adoption of microchannel heat exchangers: (1) refrigerant maldistribution inside the heat exchangers; (2) water condensate buildup on the coils, and (3) frost buildup leading to long defrost cycles. Project Duration: Sept 2007 – present.

 

Effects of Fin Design on Frost and Defrost Thermal Performances of Microchannel Heat Exchangers (Sponsor: ASHRAE)

During frosting conditions an overall heat transfer coefficient is often employed for the design and analysis of these coils due to the difficulty of separating the air-side behavior from the refrigerant-side characteristics. Previous studies showed that the outside convective thermal resistance contributes 37 to 52% of the overall thermal resistance in dry coil (initial conditions). Frost accumulation on the heat transfer area of the microchannel evaporator coils penalizes further the air-side heat transfer.

This project aims to study the effect of fin design modifications on frost and defrost thermal performance of folded fin microchannel heat exchangers. Transients case of initial frost accumulation, defrost, and subsequent re-frost cycles are going to be experimentally investigated in our air flow frosting wind tunnel. Project Duration: Sept 2009 – present.

 

Development of Design Tools for Surface Water Heat Pump Systems (Sponsor: ASHRAE, 1385-RP)

The objective of this project is to provide improved design data and design tools for SWHP systems. The scope includes collection, interpretation, and collation of design data; experimental measurement of convection coefficients on submerged heat exchangers, and development of design tools. Project Duration: Sept 2009 – present.