1 / 18

Lecture Objectives:

Lecture Objectives:. Summarize sorption chillers Learn about Chiller modeling Cooling towers and modeling. Example of H 2 O-NH 3 System. Text Book (Thermal Environmental Engineering) Example 5.5 HW 4: Solve the problem 5.6 (water – ammonia) from the textbook

whiteners
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: • Summarize sorption chillers • Learn about • Chiller modeling • Cooling towers and modeling

  2. Example of H2O-NH3 System • Text Book (Thermal Environmental Engineering) Example 5.5 • HW 4: • Solve the problem 5.6 (water – ammonia) • from the textbook • Based on example 5.5. • You may need to study example 5.6 and 5.7 • Due date is next Tuesday

  3. LiBr-H2O Systems

  4. LiBr-H2O Systems

  5. Twine vessel LiBr-H2O Systems

  6. System with no pump(Platen-Munter system) • H2O-NH3 + hydrogen http://www.youtube.com/watch?v=34K61ECbGD4

  7. Useful information about LiBr absorption chiller • http://www.cibse.org/content/documents/Groups/CHP/Datasheet%207%20-%20Absorption%20Cooling.pdf Practical Tips for Implementation of absorption chillers • Identify and resolve any pre-existing problems with a cooling system, heat rejection system, water treatment etc, before installing an absorption chiller, or it may be unfairly blamed. • Select an absorption chiller for full load operation (by the incorporation of thermal stores if necessary) as COP will drop by up to 33% at part-load. • Consider VSD control of absorbent pump to improve the COP at low load. • Consider access and floor-loading (typical 2 MW Double-effect steam chiller 12.5 tons empty, 16.7 tones operating). • Ensure ambient of temperature of at least 5°C in chiller room to prevent crystallization. • http://www.climatewell.com/index.html#/applications/solar-cooling

  8. Central chiller plant

  9. Modeling of Water Cooled Chiller (COP=Qcooling/Pelectric) Chiller model: COP= f(TCWS , TCTS , Qcooling , chiller properties) Example of a vapor compression chiller

  10. 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.

  11. Example of a chiller model http://www.comnet.org/mgp/content/chillers?purpose=0

  12. Combining Chiller and Cooling Tower Models Function of TCTS 3 equations from previous slide 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 - property of a tower 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. Cooling Towers Power plant type Major difference: NO FAN

  15. 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

  16. 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

  17. Two variable function fitting(example for a variable sped pump)

  18. Function fitting for a chillerq = f (condensing and evaporating T)

More Related