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

2. Our System

3. For Austin’s Office Building Low 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
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 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 4 8 12 16
Q= *t
Q= *t
Q [ton]
t [F]

6. Cooling Tower Performance Curve
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)
and coming in TCWR = 54F (12C)
We define power based on standard :

9. Chiller Model At the end:
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 for QNOMINAL
Available capacity as function of evaporator and condenser temperature
Cooling water supply
Cooling tower 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: 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