ZTF Electronics Cooling Michael Feeney 07 24 2017

ZTF: Electronics Cooling Michael Feeney 07. 24. 2017 M. Feeney 1

• Hardware Overview • • What equipment? Where is it located? Why do we need to cool it? • • Measured Power Required Flow Calculations • • • Chiller Electronics Rack Heat Exchanger Archon Controller Heat Exchanger • • • Serial Parallel Series-Parallel • Series-Parallel Plumbing Scheme • • Main Lines Archon Lines E-Rack HX Archon HX • • • Electronics Rack Archon Controllers Surface Temperature • Heat Dissipation • Cooling Equipment Specifications • Plumbing Schemes Introduction • Rough Circuit Analysis • Circuit Analysis • Thermal Performance • Plumbing Hardware M. Feeney 2

Archons Hardware Overview • Telescope Layout • 5 X Archon Controllers (CCD controllers) • Located at the base of the Camera Support Structure to minimize analog signal path length. • Electronics Rack • Located at the base of the telescope (reduces torque moment arm and is convenient for access). • Why cool? • To assure that the electronics are operating at safe temperature ranges. • To avoid putting warm air near the beam (convection cells) and compromising dome seeing. M. Feeney Electronics Rack 3

Hardware Overview: Electronics Rack + Electronics Rack Bud Industries 35 RU Rack + Electronics Rack Exoskeleton Misumi frame. M. Feeney Insulative Paneling Bent aluminum sheet metal components lined with insulative foam. 4

Hardware Overview: Electronics Rack Fan Tray Manufactured by Kooltronic, the fan tray is comprised of 9 X 120 mm fans capable of 945 CFM. It sits atop the heat exchanger and draws air upwards. Heat Exchanger Manufactured by Thermatron, the heat exchanger is comprised of a network of 0. 375” copper tubes with two parallel paths. The tubes zig zag a total of 20 times which creates a high surface area grid. Subsystems All of the support electronics for the various subsystems throughout the telescope sit in the rack mounted shelves or are rack mountable modules. M. Feeney 5

Hardware Overview: Electronics Rack Main Panels The main panels are made from 0. 0625” thick aluminum sheet and are lined with 2”thick insulative adhesive-backed foam. There is one panel on the tube-side of the telescope and one on the outward facing side. Misumi Rail Covers Bent aluminum sheetmetal lined with 0. 5” thick rigid insulation Access Panels The access panels are made from 0. 0625” thick aluminum sheet and lined with 1” thick adhesive-backed foam. The access panels are on either side of the rack and hinge downward when the telescope is at South stow position. They provide convenient access to the various component trays in the rack Cable Trays The electronics rack is equipped with 2 X cable trays on either side for managing the electrical cabling and plumbing. M. Feeney 6

Hardware Overview: Electronics Rack Foamcore Panels • Fan Tray Circulates Air • The fan tray draws air from the inside of the rack upwards. The air hits the top of the rack and follows the path of least resistance (2 slots out the sides). From the increased pressure, the air is forced down the sides of the rack between the insulative foam on the panels and some panels that form a channel (not shown). The air exists into the main body of the rack through two slots in the bottom and repeats the cycle. Cool Air Buffer • Natural Convection • The typical orientation of the rack is vertical (or nearly vertical). From natural convection and with the assistance of the fan tray, hot air rises to the top of the rack. M. Feeney 7

Hardware Overview: Archon Controllers The Archon Controllers mount to the telescope with a bent aluminum sheet metal bracket. Each Archon can be conveniently removed from the bracket with 4 screws. The Archons mount outside the telescope tube at the base of the camera support structure legs (4 Archons for the science CCDs and 1 Archon for the guide-focus CCDs) Coldplate Each Archon is equipped with a Lytron CP 15 G 01 cold plate which draws heat from the motherboard plane. The coldplate was modified with a threaded hole pattern such that it could be bolted securely to the motherboard plane and have solid thermal conduction. M. Feeney 8

• Hardware Overview • • What equipment? Where is it located? Why do we need to cool it? • Heat Dissipation • • Measured Power Required Flow Calculations • Cooling Equipment Specifications • • • Chiller Electronics Rack Heat Exchanger Archon Controller Heat Exchanger • Plumbing Schemes Heat Dissipation • • • Serial Parallel Combination • Rough Circuit Analysis • Combination Plumbing Scheme • Circuit Analysis • • Main Lines Archon Lines E-Rack HX Archon HX • Thermal Performance • • • Electronics Rack Archon Controllers Surface Temperature • Plumbing Hardware M. Feeney 2

Heat Dissipation: Required Flow • M. Feeney 10

• Hardware Overview • • What equipment? Where is it located? Why do we need to cool it? • Heat Dissipation • • Measured Power Required Flow Calculations • Cooling Equipment Specifications • • • Chiller Electronics Rack Heat Exchanger Archon Controller Heat Exchanger • Plumbing Schemes Cooling Equipment Specifications • • • Serial Parallel Combination • Rough Circuit Analysis • Combination Plumbing Scheme • Circuit Analysis • • Main Lines Archon Lines E-Rack HX Archon HX • Thermal Performance • • • Electronics Rack Archon Controllers Surface Temperature • Plumbing Hardware M. Feeney 2

Cooling Equipment Specs: Chiller • Manufacturer: Opti. Temp • Model Number: OTC-1. 0 with 0. 5 Hp Pump Chiller Supply vs Flow Rate 48 • Maximum Working Pressure: 90 ft (37 psi) @6 GPM Supply Pressure [psi] 46 44 42 40 38 36 34 32 30 0 1 2 3 4 Flow Rate [gpm] 5 6 7 Chiller M. Feeney 12

Cooling Equipment Specs: Electronics Rack Heat Exchanger E-Rack HX: Pressure Drop vs Flow Rate 45 40 35 Pressure Drop [psi] • Manufacturer: Thermatron • Model Number: 726 • Pressure Drop Plot is shown with water at 20 C 30 25 20 15 10 5 0 0 0. 5 1 1. 5 2 2. 5 3 Flow Rate [gpm] 3. 5 4 4. 5 5 E-Rack HX M. Feeney 13

Cooling Equipment Specs: Archon Controller Heat Exchanger Archon HX: Pressure Drop vs Flow Rate 30 25 Pressure Drop [psi] • Manufacturer: Lytron • Model Number: CP 15 G 01 • Pressure Drop Plot is shown with water at 20 C 20 15 10 5 0 0 0. 2 0. 4 0. 6 0. 8 Flow Rate [gpm] 1 1. 2 1. 4 Archon HX (1 X) M. Feeney 14

• Hardware Overview • • What equipment? Where is it located? Why do we need to cool it? • Heat Dissipation • • Measured Power Required Flow Calculations • Cooling Equipment Specifications • • • Chiller Electronics Rack Heat Exchanger Archon Controller Heat Exchanger • Plumbing Schemes • • • Serial Parallel Combination • Rough Circuit Analysis • Combination Plumbing Scheme • Circuit Analysis • • Main Lines Archon Lines E-Rack HX Archon HX • Thermal Performance • • • Electronics Rack Archon Controllers Surface Temperature • Plumbing Hardware M. Feeney 2

Plumbing Schemes: Serial • Advantages: • Simple plumbing • Disadvantages: • Big pressure drop • Considerable temperature difference between Archons Archon Supply Branch ID: 0. 27 Length: 6 ft Archon Return Branch ID: 0. 27 Length: 6 ft Main Supply Line ID: 0. 75” Length: 50 ft Chiller Opti. Temp OTC-1. 0 Electronics Rack Heat Exchanger Thermatron 726 Model Main Return Line ID: 0. 75” Length: 50 ft M. Feeney 16

Plumbing Schemes: Parallel Archon Return Branch (QTY 2) ID: 0. 270 Length: 6 ft Archon Supply Branch (QTY 2) ID: 0. 270 Length: 6 ft Main Supply Line ID: 0. 75” Length: 50 ft Chiller Opti. Temp OTC-1. 0 Electronics Rack Heat Exchanger Thermatron 726 Model Main Return Line ID: 0. 75” Length: 50 ft M. Feeney • Advantages: • Uniform temperature for all Archons • Disadvantages: • Complicated plumbing scheme 17

Plumbing Schemes: Series-Parallel (not too hot, not too cold) Archon Return Branch 2 ID: 0. 270 Length: 10 ft Archon Return Branch 1 ID: 0. 270 Length: 6 ft Archon Supply Branch 2 ID: 0. 270 Length: 10 ft Archon Supply Branch 1 ID: 0. 270 Length: 6 ft Main Supply Line Main Return Line ID: 0. 75” Length: 50 ft Chiller Opti. Temp OTC-1. 0 Flow: 1 -10 GPM @34 psi M. Feeney 18

• Hardware Overview • • What equipment? Where is it located? Why do we need to cool it? • Heat Dissipation • • Measured Power Required Flow Calculations • Cooling Equipment Specifications • • • Chiller Electronics Rack Heat Exchanger Archon Controller Heat Exchanger • Plumbing Schemes Rough Circuit Analysis • • • Serial Parallel Series-Parallel • Rough Circuit Analysis • Series-Parallel Plumbing Scheme • Circuit Analysis • • Main Lines Archon Lines E-Rack HX Archon HX • Thermal Performance • • • Electronics Rack Archon Controllers Surface Temperature • Plumbing Hardware M. Feeney 2

Rough Circuit Analysis: Parallel: Q = Q 1 + Q 2 + Q 3 ∆P 1 = ∆P 2 = ∆P 3 Serial: Q 1 = Q 2 = Q 3 ∆P = ∆P 1 + ∆P 2 + ∆P 3 Series Parallel Assuming 6. 5 GPM ∆P = 36. 5 psi = ∆P 3+ ∆P 4+ ∆P 5 Neglecting the pressure drop in the lines, it is assumed all 36. 5 psi makes it to this branch of the Archon Heat Exchangers. Since each heat exchanger is identical, the pressure drop across each is equivalent (12. 1 psi). the max flow rate can be ~1. 2 gpm (see plot). Assuming 6. 5 GPM ∆P = 36. 5 psi = ∆P 1+ ∆P 2 Neglecting the pressure drop in the lines, it is assumed all 36. 5 psi makes it to this branch of the Archon Heat Exchangers. Since each heat exchanger is identical, the pressure drop across each is equivalent (18. 25 psi). the max flow rate can be ~1. 3 gpm (see plot). Assuming 6. 5 GPM ∆P = ∆P E = 36. 5 psi Neglecting the pressure drop in the lines, it is assumed all 36. 5 psi makes it to this branch of the Rack Heat Exchanger and the resultant flow is ~4. 5 gpm. 36. 5 psi 6. 5 GPM Good initial estimates, but what about loss in lines? M. Feeney 20

• Hardware Overview • • What equipment? Where is it located? Why do we need to cool it? • Heat Dissipation • • Measured Power Required Flow Calculations • Cooling Equipment Specifications • • • Chiller Electronics Rack Heat Exchanger Archon Controller Heat Exchanger • Plumbing Schemes Circuit Analysis • • • Serial Parallel Combination • Rough Circuit Analysis • Combination Plumbing Scheme • Circuit Analysis • • Main Lines Archon Lines E-Rack HX Archon HX • Thermal Performance • • • Electronics Rack Archon Controllers Surface Temperature • Plumbing Hardware M. Feeney 2

Circuit Analysis: Main Lines • Main Line Diameter [in] 0. 75 Main Line Length [ft] 170 Pressure Drop [psi] Main Line: Pressure Drop vs Flow Rate 20 15 Non-negligible pressure drop 10 5 0 0 1 2 3 4 5 Flow Rate [gpm] 6 7 8 9 Main Line M. Feeney 22

Circuit Analysis: Archon Lines • Archon Line Diameter [in] 0. 25 Archon Branch 1 Line Length [ft] 12 Archon Branch 2 Line Length [ft] 20 Pressure Drop [psi] Archon Lines: Pressure Drop vs Flow Rate 10 8 6 4 Still Non-negligible pressure drop 2 0 0 0. 2 0. 4 0. 6 0. 8 Flow Rate [gpm] Archon Line 1 (12 ft) 1 1. 2 1. 4 Archon Line 2 (20 ft) M. Feeney 23

Circuit Analysis: Main Lines + E-Rack HX E-Rack Branch: Pressure Drop vs Flow Rate e-rack hx [gpm] • 4 GPM through E-Rack HX • 2. 1 GPM through Archons. • 9 psi loss in Main Line Pressure Drop [psi] • 2. 1 GPM was assigned to the Archon paths. • Total Flow: 6. 1 GPM 60 0 0. 5 1 1. 5 2 50 2. 5 3 3. 5 4 4. 5 5 Chiller Operating Pressure 40 30 20 10 0 9 psi 0 1 2 3 4 Main Line & Chiller [gpm] 5 6 Main Line + 2. 1 gpm Archon Chiller Supply E-Rack HX E-Rack + Main Line M. Feeney 7 24

Circuit Analysis: Main Lines + Archon HX 60 50 40 30 20 10 0 Archon Branch 2: Pressure Drop vs Flow Rate Pressure Drop [psi] Archon Branch 1: Pressure Drop vs Flow Rate Plus Main Line ΔP 9 psi 0 0. 2 Archon Line 0. 4 0. 6 0. 8 Flow Rate [gpm] 1 Archon Heat Exchanger (2 X) 1. 2 1. 4 60 50 40 30 20 10 0 Total Plus Main Line ΔP 9 psi 0 0. 2 Archon Line Branch Flow [GPM] E-Rack Branch 4 Archon Branch 1 1. 15 Archon Branch 2 0. 95 Total 6. 1 M. Feeney 0. 4 0. 6 0. 8 Flow Rate [gpm] 1 Archon Heat Exchanger (3 X) 1. 2 Total 25 1. 4

Circuit Analysis: Summary ∆P = 24. 5 psi, 0. 95 GPM ∆P = 25 psi @ 1. 15 GPM ∆P = 29 psi, @4 GPM ∆P = 4. 5 psi ∆P = 4 psi ∆P = 9 psi M. Feeney 26

• Hardware Overview • • What equipment? Where is it located? Why do we need to cool it? • Heat Dissipation • • Measured Power Required Flow Calculations • Cooling Equipment Specifications • • • Chiller Electronics Rack Heat Exchanger Archon Controller Heat Exchanger • Plumbing Schemes Thermal Performance • • • Serial Parallel Combination • Rough Circuit Analysis • Combination Plumbing Scheme • Circuit Analysis • • Main Lines Archon Lines E-Rack HX Archon HX • Thermal Performance • • • Electronics Rack Archon Controllers Surface Temperature • Plumbing Hardware M. Feeney 2

Thermal Performance: Archon Controllers • M. Feeney 28

Thermal Performance: E-Rack HX M. Feeney 29

Thermal Performance: Fluid Temp Rise ∆T = 2. 1°C, 0. 95 GPM ∆T = 1. 27°C @ 1. 15 GPM ∆T = 1. 4°C, @4 GPM M. Feeney 30

Thermal Performance: Electronics Rack Air Temperature • M. Feeney 31

Thermal Performance: Te Electronics Rack Surface Temperature Ta • Ti ERack Surface Temperature vs Ambient Temperature 3. 5 3 T_e-T_a [K] 2. 5 2 1. 5 T_a = 273 K T_a = 285 K T_a = 295 K T_a = 305 K 1 0. 5 0 0 10 20 T_i-T_a [K] 30 M. Feeney 40 32

• Hardware Overview • • What equipment? Where is it located? Why do we need to cool it? • Heat Dissipation • • Measured Power Required Flow Calculations • Cooling Equipment Specifications • • • Chiller Electronics Rack Heat Exchanger Archon Controller Heat Exchanger • Plumbing Schemes Plumbing Hardware • • • Serial Parallel Combination • Rough Circuit Analysis • Combination Plumbing Scheme • Circuit Analysis • • Main Lines Archon Lines E-Rack HX Archon HX • Thermal Performance • • • Electronics Rack Archon Controllers Surface Temperature • Plumbing Hardware M. Feeney 2

Plumbing Hardware Main Line Plumbing • Parker QDCs • Parker flexible line Archon Plumbing: • QDCs stem and body shutoffs • PTFE lined SS braided hoses M. Feeney 34

Conclusions • These are theoretical calculations • Will need to be confirmed through testing • All calculations made at 20 C. • Pressure drops will increase with increased viscosity. • Fluid flow pressure drops are non-linear. Not as easy as electrical engineering • Electrical Engineering is easier than Plumbing M. Feeney 35