cfac review –

1 BROOKHAVEN SCIENCE ASSOCIATES

CFAC Review –

Chris Channing P.E.Sr Project Engineer

NSLS-II Conventional Facilities - Thermal StabilityMay 8, 2007


Temperature stability goals

• Key temperature stability requirement is tunnel air @ +/- 0.1C (+ /-.18 F) at any given location over 1 hour• Key parameter is temperature stability and repeatability

vs. absolute accuracy.

• Tunnel temperature of 78 was selected to eliminate the concern of a temperature gradient between the experimental floor and the tunnel.

• The tunnel air conditioning system will be designed to accommodate tunnel temperatures between 75 and 85 F. During commissioning period, tests will be conducted to determine the optimum tunnel setpoint temperature.


Temperature stability

• The following will be done to achieve the requirements.• Requires high resolution industrial grade instruments and controls with

excellent repeatability. Will use narrow span thermistor/transmitters with .01 C sensitivity.

• Control scheme using programmable controllers with 14 bit resolution. • We will use a control program we have written which reset the discharge air

temperature in response to room temperature deviation from setpoint. The program resets and controls discharge air temperature to find the exact supply temperature required to satisfy the load requirements. This minimize the temperature fluctuation in the room. We have several application were we currently use this concept to achieve +/- 0.1C control.

• We will use electric reheat with SCR control to allow for fast accurate control of discharge air temperature.


Temperature Stability cont.

• It is not envisioned that the economizer will be used during beam mode to keep stable tunnel conditions.

• Should be readily achievable provided loads to accelerator components are relatively steady-state.

• We are working with APS to modify a section of their tunnel system to prove out our concept.

• We will also be investigating thermal modeling of the tunnel equipment and air flows to verify our assumptions.


Tunnel Temperature Control


Tunnel Air Distribution


Tunnel Supply Duct


Tunnel Return Duct


Example of control system stability

70

65

60



71

71.2

70.8



65

60

DASHED CURVE IS REQUIRED DISCHARGE AIR SET POINT TO MEET LOAD

ON TOP OF IT IN YELLOWIN YELLOW IS ACTUAL DISCHARGE AIR SETPOINTSYSTEM CONTROLLED TO.

TEMPERATURES IN DEGREES F


Path Forward• Pursuing several paths to validate approach to thermal stability • Working with APS to modify a section of APS tunnel to simulate the proposed

system and perform control and measurements of the modified system.• Our concepts are included in the new CFN Building

• Will use information learned to prove out and refine our concepts. • Currently starting up and commissioning these systems.

• Evaluating thermal modeling software • Leaning toward Fluent Ansys Airpak software for CFD modeling of tunnel airflow • Additional thermal modeling using Thermo Analytics Rad Therm software that will take

into account radiant, conduction and convection heat transfer effects. Rad Therm allows for direct importing from Fluent software.

• Due to learning curve for software, may use consulting services from these companies to for initial set up and modeling while we learn how to use it

• This will allow us to make changes to the model as the design progresses and evolves. • Will use data from APS tunnel measurements and CFN measurement to validate

the models and software.• We are evaluating different supply and return flow configurations.

• Will use the CFD/thermal modeling software to help optimize the air distribution systems.

cfac review –

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