Cooling a Mobile Radar Shelter Saab Defense and Security. Peter Ruzicka October 07,2014 SAAB DEFENSE AND SECURITY USA, LLC

Transcription

1 Cooling a Mobile Radar Shelter Saab Defense and Security Peter Ruzicka October 07,2014 SAAB DEFENSE AND SECURITY USA, LLC The information in this document is proprietary to, and the property of Saab Defense and Security USA, LLC. It may not be duplicated, used, or disclosed in whole or in part for any purpose without express written consent. Saab Defense and Security USA, LLC 2013

2 Sensor Systems Portfolio USMC G/ATOR Teamed with Northrop Grumman Multi-function 3D Expeditionary Radar Replaces 5 Legacy radars Supports Maneuver Warfare Sea Giraffe AMB Naval Radar Multi-function Radar Aboard LCS Air/Surface Surveillance Tracking Target ID/Cueing For Weapon Systems Excellent Low RCS Target Detection USAF/USMC 3DELRR Teamed with multiple Primes First functional prototype <18 months Composites for expeditionary missions Single vehicle containment Small Scale Radar RF solution for Hostile Fire Detection Small Arms (5.56/7.62/50 Cal), and RPG Detection Small Lightweight for vehicle, watercraft, or fixed site applications Radar Upgrades Same or better performance at a fraction of the cost of a replacement radar COTS/OA Architecture Multi-Band Global Installations Ground and Naval Systems Carabas FOPEN/GPEN SAR Multi-Band SAR Technology Enhances ground penetration at low band and improves resolution at high band Scalable for future UAV deployment GIRAFFE Multi-Mission Surveillance System Small target performance in all conditions High mobility and survivability Being deployed by Dept. of State

3 Saab Defense and Security Spectrum of Radar Experience Radar Modernization and Sustainment Significant experience with foreign radar designs and upgrades OEM host nations were U.S., Russia, and U.K. Modernized 18 different types of Radars in 14 different countries All without support from Original Equipment Manufacturer Next Generation Radar Design and Development USAF 3DELRR TD Phase Prime prototype in 19 months: L-Band AESA Key subcontractor to Northrop Grumman on USMC G/ATOR radar R&D Investment in next generation radar technology building blocks Open Architecture Radar Library in Development Saab Radar Systems Saab Sensis is the Radar House for Saab AB in the U.S. Sea Giraffe for the Navy, Land Giraffe for Dept of State Supports entire Saab radar portfolio in the U.S. Access to significant radar technology in various freq. bands and mission sets

4 Design of a Mobile equipment shelter The information in this document is proprietary to, and the property of Saab Defense and Security USA, LLC. It may not be duplicated, used, or disclosed in whole or in part for any purpose without express written consent. Saab Defense and Security USA, LLC 2013

5 Two System Developed Roof top Radar Installation Ground based Radar Installation

6 Roof Top Load Structures Views of Roof top Installation

7 Container Assembly Exterior View Main Components Identified. Opening and Support for Supplemental A/C unit Power, Signal and Waveguide Output 2 access doors Opening for Power Input Panel

8 Detailed Design Considerations High Ambient air temperatures in summer seasons with the seasonal high average of 44 C. Maximum solar loading in the region of over 500 watts/m 2. Electro-Magnetic Interference (EMI) design requirements. High reliability and availability are critical for protection. Provide environmental shelter protection for critical electronic equipment.

9 Initial Concept Design Issues and Challenges When I was brought onto the design team and reviewed the initial concept design I was able to recognize some key short comings: The Initial sizing of the Air Conditioning Unit did not include the environmental thermal loading and that the AC unit being a long lead item was already ordered was undersized. The need for service personnel to have adequate ventilation of fresh air was overlooked. The EMI requirement was challenged because of the through wall piercings for the AC unit refrigerant lines to the evaporator resulted in a area of EMI ingress/egress.

10 Design Changes to Overcome the Issues and Challenges. I addressed the EMI Ingress/Egress concern by bringing the Compressor and Condenser package into the EMI Envelope by using EMI Honey Comb filters that would provide the needed shielding and still allow for the air flow required by the condenser fan. I added a ventilation system that was capable of providing the needed fresh air as determined by OSHA requirements for two service personnel. This system was controlled by dampers and a fan that would be turned on with the inside illumination when service personnel entered the container and go off and close when the personnel left and turned off the lights.

11 EMI Honey Comb Air Filter with Protective Grill

12 Design Changes to Overcome the Cooling Issues and Challenges. I validated my suspected claim that the current two packaged AC unit was not capable to cool the container by using a Back of the Envelope hand calculation using the ACCA Manual J worksheet. Determined that a supplemental AC unit was required. The supplemental AC unit was oversized to allow for high temperature operation degradation and to provide design margin for reliability.

13 Back of the Envelope Calculation Heat Loads Component Heat Emission to the Containerized system Cooling Air (kw) Heat Emission to the Containerized system Cooling Air (BTU/Hr) Climate System Air Handler (FAU) Sensor TRU + Stand by SDU Two Lap Tops RIU TT VDC Timeserver IFF Interrogator IFF Booster Power Loss DC Conversion Miscellaneous DAU Battery Charger Power Distribution One Person Environmental Heat Gain Totals

14 ACCA Manual J Worksheet The Initial sized unit was only rated at 2.8 Tons (10kW) of AC Cooling Capacity. This Indicated the need for a Supplemental AC Unit for the Total Cooling Load.

15 Block Diagram of AC Cooling of Container Equipment Air Flow Room Air Filter Air Flow in from Room Air Handler (Blower) Air Flow Supplemental AC Unit Supplemental AC Unit Recirculation of Room Air During Operation TRU Air Flow SDU Air Flow to Room Air Flow HVAC Condensor Unit Evaporator Unit

16 Container AC Unit Placement and Wall Insulation

17 Container Details

18 Cooling Units and Container Insulation Values Subcomponent Description Cooling Capacity Weiss ZKB 15/10-SH Main Air Conditioning Unit (Split Pack) 2.8 Tons (10 kw) Friedrich Hazardgard SH20 Owens Corning Foamular 150 Extruded Polystyrene Rigid Foam Insulation Supplemental Air Conditioning Unit (window unit) Rigid Foam Insulation utilized in walls and ceiling of container 1.6 Tons (5.7 kw) R-5 per inch

19 Container Cooling Issue When the system was deployed we quickly identified a cooling air distribution issue! Air circulation within the container is not sufficient to get the cool air to where it is needed most! The Container had a cool end and a hot end! The cool air circulates at one end of the container, while the warm air circulates at the other end! Resulting in SDU temperature warnings and faults! Before illustration of heat flow

20 Container Cooling Air Distribution Solutions Created a computer simulation model to investigate the potential solution of adding air flow directing duct work tothe Transmitter Unit (TRU) and the Signal Data Unit (SDU). Needed to validate that there indeed was sufficient air conditioning capacity. Needed to show system would operate in the extreme hot environmental conditions and eliminate SDU over temperature warnings and faults.

21 Container Modeling The container was modeled and represented by a thick steel shell, with 3 inches thick foam insulation of (R- 5/inch) along the exterior walls and 1/8 inch wood paneling with the foyer room having only 1 inch thickness between the adjacent wall of the equipment room. The floor was represented by a steel plate with a 1/8 inch surface that was left un-insulated. The heat loads were assigned to representative models for the equipment and assigned the values from Table on Slide 13. The thermal loads for the SDU and TRU were modeled using the thermal dissipative power assigned to a low flow resistance porous media representation; airflow through these devices was modeled using constant flow fan representations.

22 Container Modeling - Continued The air handler thermal contribution was handled again with the porous media representation with the associate thermal load assigned. Airflow through the air handler was accomplished by modeling the connecting ductwork. To realize results of the air intact of the air handler a porous media grill was created at the entrance opening to allow for the results of the surface parameters within the software output. The airflow for the SDU was fixed at 147 CFM and the flow rate through the TRU rep was set to 500 CFM. The main air condition and the supplemental air conditioners were modeled again using a porous media with the assigned cooling capacity as a negative power in total watts and the airflow through each assigned using fixed flow fan models.

23 Container Modeling - Continued Air Conditioning Unit Modeling The main AC is a Weiss model number ZKB 15/10-SH with a cooling capacity of 10,000 watts and supply air flow of 1,900 m3/hr (~1120 CFM). The supplemental AC a Friedrich Hazardgard 20 with BTU/hr or approximately 5714 watts. (1 BTU/hr watts). This modeled unit representation was assigned a cooling capacity of 5700 watts with supply airflow of 425 CFM. The air flow rates were derived directly from the specification sheet for each of the AC units.

24 Container Modeling - Continued Environmental Boundary Conditions - container were that all external surface were assigned a constant temperature of 44 C with the exception of the top surface that was assigned a power of 501 w/m 2 surface generation power. This value was obtained from an online academic reference titled Estimation of Global Solar Radiation on Horizontal Surface Using Routine Meteorological Measurements for Different Cities in Iraq the location of this on the web is:

25 Container Modeling - Continued Environmental Boundary Conditions - In the reference document, Estimation of Global Solar Radiation on Horizontal Surface Using Routine Meteorological Measurements for Different Cities in Iraq, indicated that the peak monthly daily solar radiation occurs in the month of June with a value of M J/m 2 /day or about 313 w/m 2 for this location. In the real world, the daily temperatures along with the solar radiation values are transient values. MODELING ASSUMPTION-By using the geographical maximum value of 501 w/m 2 value and assuming full absorption with a maximum outside temperature of 44 C as a steady state condition, this should result in a worstcase approximation and be very conservative by over estimating the internal air temperatures.

26 Container Modeling - Continued Porous Media Thermal Load Porous Media Intake Air TRU Air Handler SDU The porous media model was used to represented the heat load of each device. The air handler model used the porous media at the inlet to simulate air intake filter and to obtain modeling results, and at the duct entrance for the thermal load. Porous Media Thermal Load

27 Container Modeling - Continued The remaining heat producing equipment was modeled and placed in the proper position within the container. The associated heat loads were also applied to the equipment models.

28 Container Modeling - Continued Main AC Unit Evaporator The main AC and supplemental unit were modeled using porous media with a negative heat load, with the air flow assigned to each model rep with fixed flow fans as determined by the unit specification sheet. Supplemental AC Unit

29 Container Modeling - Continued The container model included the materials of construction in layers that were modeled a solids. This gives more accurate through wall heat transfer but has a cost of processor time and memory. Solar loading was applied as a distributive heat load over the top surface area. The remaining outside walls of the container were assigned the environmental temperature boundary condition.

30 Simulation Results This worst case simulation resulted in an average air inlet temperature of the modeled air handler of 14 C with a minimum temperature of 12 C, and a maximum inlet temperature of 19.1 C, within required limit of 20 C. The average air temperature including the un-cooled and un-insulated foyer volume was 22.7 C. There was no mixing fan in this simulation and the air mixing was all due to the modeled fans in the AC units and those modeled fans within the forced air-cooled path with the directing exit air ducts. PAGE 30

31 Simulation Results - Continued

32 Simulation Results - Continued

33 Simulation Results - Continued

34 Simulation Results - Continued The top surface temperature gradients are due to the distributed solar load of 500 w/m 2 and note that surface temperature peaks to approximately 215 C. This does not include any convection or radiation heat loss to the environment and is very conservative. Steady state condition is the sun is beating down onto roof continually, in the real world this is a transient condition.

35 Prototyped Modifications to Validate Simulation 1) TRU Exhaust Ducting Directs warm exhaust air down and away from the blower inlet THIS IS THE MOST IMPORTANT MODIFICATION 2) SDU Exhaust Ducting Directs warm exhaust air down and away from the blower inlet and away from the TRU ANTHER IMPORTANT MODIFICATION 3) Circulating Fan (Added as an Enhancement) Directs cool air from the a/c system directly towards the blower air inlet Creates circulation Study shows this is really not needed, but was added to increase air mixing.

36 Verified Effectiveness of Cooling Fix on Site Once cooling modifications were in place on the typical summer day of 38 C at high sun. Set thermostat in room at 20 C Turned off secondary AC Allow room temperature to stabilize Door closed Preferably lights off so outside air is not circulating through container (outside air ventilation system off). Measure temperature of cooling air with IR thermometer (or equivalent) Was approximately 20 C (66F) entering blower SDU/TRU air duct will also measure approximately 20 C (66 F) Secondary AC will be on and used to supplement cooling in the extreme hot ambient temperatures of 44 C plus and with added heat load due to incident solar radiation.

37 Questions? I know I did not speak to any of these Topics. But in the air conditioner world what is meant by Sensible Heat? What is the difference between the total cooling capacity and the sensible heat load. What does Dew Point mean in the air conditioner world, and what issues does it present? What are the variables that determine the operating temperature range of an air conditioning unit? What causes the cooling performance degradation with temperature?

38 My contact information Peter J. Ruzicka Senior Mechanical Engineer Sensor Systems Saab Defense and Security USA, LLC 5717 Enterprise Parkway East Syracuse, New York Phone: (315) , Fax: (315)