1 / 14

Lecture Objectives:

This lecture discusses the Project 1 assignment and introduces topics for the Final Project on low-order building modeling and chiller performance analysis. Topics include determining Q(τ) for each hour, cooling tower performance curve, chiller modeling, and more.

mphipps
Télécharger la présentation

Lecture Objectives:

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Lecture Objectives: • Discuss Project 1 assignment • Introduce some topics for the Final Project

  2. Our System

  3. For Austin’s Office BuildingLow Order Building Modeling Model: (Area = 125,000sf) Hours in a year kW Used for component capacity analysis Model =0 when building is off Number of hours

  4. Low Order Building Modeling Measured data or Detailed modeling Find Q() = f (DBT)

  5. For project 1 you will need Q()for each hour 20 16 12 Q [ton] Yearly based analysis: You will need Q() for one week in July Use simple molded below and the Syracuse TMY3 weather file posted in the course handout section 8 Q=--27.48+0.5152*t 4 Q=-0.45 +0.0448*t 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 t [F]

  6. Cooling Tower Performance Curve R TCTR Outdoor WBT from chiller TCTS to chiller Temperature difference: R= TCTR -TCTS TCTS Most important variable is wet bulb temperature TCTS = f( WBToutdoor air , TCTR , cooling tower properties) or for a specific cooling tower type TCTS = f( WBToutdoor air , R) WBT

  7. Cooling Tower Model Model which predict tower-leaving water temperature (TCTS) for arbitrary entering water temperature (TCTR) and outdoor air wet bulb temperature (WBT) Temperature difference: R= TCTR -TCTS Model: For HW 3b: You will need to find coefficient a4, b4, c4, d4, e4, f4, g4, h4, and i4 based on the graph from the previous slide and two variable function fitting procedure

  8. Chiller Example: ANSI/AHRI STANDARD Defines standardl Pelc for standard Qcooling for standard conditions (defines COP nominal) Standard for air cooled chiller testing: Air entering the condenser is T out. air = 95F (35C) Water leaving the evaporator is TCWS= 44F (6.5 C) and coming in TCWR= 54F (12C) Standard for water cooled chiller testing: Water entering the condenser is TCTS= 85F (29C) leaving TCTR = 95F (35C) Water leaving the evaporator is TCWS= 44F (6.5 C) and coming in TCWR = 54F (12C) We define power based on standard :

  9. Chiller Model Correction for having different nominal and standard conditions Cooling CApacity Factor as Function of Temperature - CAPFT It is equal to when design conditions are equal to nominal condition Correction for not having different operation condition over time (Electric Input to Cooling Output Ratio Function of Temperature - EIRFT) It is equal to 1 when WBT is equal to design condition (it is function of time) Correction for not different cooling load Energy Input to Cooling Output Ratio Function of Part Load Ratio Curve - EIRFPLR At the end:

  10. Modeling of Water Cooled Chiller (COP=Qcooling/Pelectric) Chiller model: COP= f(TCWS , TCTS , Qcooling , chiller properties)

  11. Modeling of Water Cooled Chiller Chiller model: Chiller data: QNOMINAL nominal cooling power, PNOMINAL electric consumption forQNOMINAL Available capacity as function of evaporator and condenser temperature Cooling tower supply Cooling water supply Full load efficiency as function of condenser and evaporator temperature Efficiency as function of percentage of load Part load: The consumed electric power [KW] under any condition of load The coefiecnt of performance under any condition Reading: http://apps1.eere.energy.gov/buildings/energyplus/pdfs/engineeringreference.pdf page 597.

  12. Combining Chiller and Cooling Tower Models For your problem Function of WBT 3 equations from previous slide Function of TCTS Add your equation for TCTS → 4 equation with 4 unknowns (you will need to calculate R based on water flow in the cooling tower loop)

  13. Merging Two Models Temperature difference: R= TCTR -TCTS Model: Link between the chiller and tower models is the Q released on the condenser: Q condenser = Qcooling + Pcompressor - First law of Thermodynamics Q condenser = (mcp)water form tower (TCTR-TCTS) m cooling tower is given through TCTR for design condition TCTR= TCTS - Q condenser / (mcp)water Finally: Find P() or The only fixed variable is TCWS = 5C (38F) and Pnominal and Qnominal for a chiller (defined in nominal operation condition: TCST and TCSW); Based on Q() and WBT you can find P() and COP().

  14. Final Project • Expand this Project • Variable speed pumps • Different type of chillers • Different buildings • …. • Modeling of processes in the psychrometric chart • Will discuss next week

More Related