New Way of Using Flovent for Effective Data Center Analysis: The Rack Cooling Index (RCI) Flomerics Web Presentation October 4, 2006

Transcription

1 New Way of Using Flovent for Effective Data Center Analysis: The Rack Cooling Index (RCI) Flomerics Web Presentation October 4, 2006 Magnus K. Herrlin, Ph.D., CEM President Incorporated Copyright (c) 2006 by Inc. 1

2 Environmental & Energy Solutions Dr. Magnus K. Herrlin is President of Incorporated, a San Francisco based consultancy providing advanced indoor environmental and energy solutions for mission critical facilities. Please visit Copyright (c) 2006 by Inc. 2

3 Challenge CFD modeling allows visualization of temperatures throughout the data center. Still, to sort out the cooling effectiveness of different design options can be challenging. By using the same CFD technology, the rack intake temperatures can be established. These temperatures provide a picture of the thermal environment but there is no yardstick for interpreting the conditions. The Rack Cooling Index (RCI) has the capacity to change this state of affairs. The RCI is a measure of how effectively equipment is cooled and maintained within industry thermal guidelines. This presentation demonstrates how Flovent modeling and the RCI can enhance the data center design work (consultants) or serve as a design specification (owners/operators). Copyright (c) 2006 by Inc. 3

4 Importance of Intake Temperatures The main task for a data center facility is to provide an adequate equipment environment; a relevant metric for equipment intake temperature should be used to gauge the thermal environment. Temperature not important Temperature not important Temperature important (rack intake) Front Rear Side View of Rack Copyright (c) 2006 by Inc. 4

5 CFD Model Intake Temperatures CFD modeling establishes the temperature, velocity, and pressure fields in the equipment room, including intake temperatures. Large data center with over-head cooling (55) (70) (84) (99) (113) Approximate Scale C ( F) Cross-section with temperatures Copyright (c) 2006 by Inc. 5

6 Temperature Specifications Compliance with intake temperature specifications is the ultimate cooling performance metric; the Rack Cooling Index (RCI) is such a metric. Eliminating red (hot) and blue (cold) areas RCI = 100% Rack Intake Temperature Intake temperatures arranged in order of increasing temperature Max Allowable Max Recommended Hot Min Recommended Min Allowable Recommended Range Cold Rack Intake # Copyright (c) 2006 by Inc. 6 N

7 Rack Cooling Index (RCI) Compliance with intake temperature specifications at the upper extreme is called RCI(HI) and the compliance at the lower extreme is called RCI(LO). Both at 100% mean ideal conditions. Max Allowable Max Recommended Min Recommended Min Allowable Rack Intake Temperature Recommended Range Intake temperatures arranged in order of increasing temperature Total Over-Temp RCI(HI) = 95% Total Under-Temp RCI(LO) = 35% Rack Intake # Copyright (c) 2006 by Inc. 7 N

8 How Is RCI Calculated? The Rack Cooling Index (RCI) can easily be calculated manually or by using RCI software (future CFD codes may do this too). RCI Software Copyright (c) 2006 by Inc. 8

9 What Is Considered a Good RCI? The ratings below are based on a number of modeling studies. Since the interpretation of the RCI is straight forward, it does not require an in-depth understanding of the definition (reference below). Rating RCI Ideal 100% Good 91% Acceptable 81-90% Poor 80% Reference: Herrlin (2005) Herrlin, M. K Rack Cooling Effectiveness in Data Centers and Telecom Central Offices: The Rack Cooling Index (RCI) ASHRAE Transactions, Volume 111, Part 2 (Free download at Copyright (c) 2006 by Inc. 9

10 What Can RCI Be Used For? Design Equipment Environments. CFD modeling combined with the RCI provides a standardized method for evaluating and reporting environmental and energy solutions. Provide Design Specifications. Clients now have the opportunity to specify a certain level of thermal comfort in an objective and standardized way, e.g., RCI > 95%. Monitor Equipment Environments. Real-time monitoring of the environment is feasible by installing temperature sensors that mimics the equipment intake conditions. Help Product Development/Marketing: The RCI can effectively help demonstrate the benefit of a cooling solution. A product or solution with an RCI at or near 100% should be marketed as such. Copyright (c) 2006 by Inc. 10

11 The Process Step-by-Step Step 1: Establish a Flovent model of the data center Step 2: For each design variation, determine equipment intake temperatures Step 3: Export the temperatures to your favorite spread sheet or data base program Step 4: Calculate RCI manually or use RCI software (future CFD codes may do this for you) Step 5: Compare RCI for the different design options, the closer to 100%, the better. Copyright (c) 2006 by Inc. 11

12 Let s Look at Two Examples We will compare over-head cooling with traditional under-floor (raised-floor) cooling. Example 1: Organized environments with hot/cold equipment aisles. Example 2: Mixed environments with no hot/cold equipment aisles. Copyright (c) 2006 by Inc. 12

13 Example 1 Organized environments with hot/cold equipment aisles. VUF Modular-OH Reverse-VUF Reference: Herrlin and Belady (2006) Herrlin, M. K. and Belady, C Gravity-Assisted Air Mixing in Data Centers and How it Affects the Rack Cooling Effectiveness. IEEE-ITherm 2006, San Diego, CA, May 30 June 2, 2006 (Free download at Copyright (c) 2006 by Inc. 13

14 Example 1 In the organized equipment environments with hot/cold aisles, over-head cooling outperforms vertical under-floor (VUF) cooling Rack Cooling Index (RCI) [%] Modular-OH Top-Down Reverse-VUF Reverse-Tile VUF Bottom-Up 0 RCI(HI) RCI(LO) Copyright (c) 2006 by Inc. 14

15 Example 2 Mixed environments with no hot/cold equipment aisles. Under-Floor Cooling (VUF) Over-Head Cooling (VOH) Copyright (c) 2006 by Inc. 15

16 Example 2 Also in the mixed environment with no hot/cold aisles, vertical over-head (VOH) cooling performs better Rack Rack Cooling Index (RCI) [%] [%] VOH VUF 0 50 W/ft2, Design 1 50 W/ft2, Design W/ft2, Design W/ft2, Design 2 Cases Copyright (c) 2006 by Inc. 16

17 Summary By using the described Rack Cooling Index (RCI) it was shown that over-head cooling is more effective than raised-floor cooling. These differences would have been difficult to uncover without the use of the RCI in conjunction with CFD modeling. The step-by-step process of determining the cooling effectiveness is simple and quick by using Flovent and RCI software. Copyright (c) 2006 by Inc. 17

18 Thank You Dr. Magnus K. Herrlin Copyright (c) 2006 by Inc. 18