lecture objectives: introduce hw3 learn about sorption chillers
DESCRIPTION
HW3 Writhe a sequence of operation instruction list for the air handling unit from HW2 (problems: 3&4)TRANSCRIPT
Lecture Objectives:
• Introduce HW3
• Learn about sorption chillers
Sequence of operation(PRC research facility)
Control logic:
Mixture in zone 1: IF (( TM<TSP) & (DPTM<DPTSP) ) heating and humidifying Heater control: IF (TSP>TSA) increase heating or IF (TSP<TSA) decrease heatingHumidifier: IF (DPTSP>DPTSA) increase humidifying or IF (DPTSP<DPTSA)
decrease humid.
Mixture in zone 2: IF ((TM>TSP) & (DPTM<DPTSP) ) cooling and humidifying Cool. coil cont.: IF (TSP<TSA) increase cooling or IF (TSP>TSA) decrease
coolingHumidifier: IF (DPTSP>DPTSA) increase humidifying or IF (DPTSP<DPTSA)
decrease hum.
Mixture in zone 3: IF ((DPTM>DPTSP) ) cooling/dehumidifying and reheatinCool. coil cont.: IF (DPTSP>DPTSA) increase cooling or IF (DPTSP<DPTSA)
decrease cooling Heater control: IF (TSP>TSA) increase heating or IF (TSP<TSA) decrease heating
Set Point (SP)
Mixture 2
Mixture 3
Mixture 1
DBTSP
DPTSP
HW3
• Writhe a sequence of operation instruction list for the air handling unit from HW2 (problems: 3&4)
HW3• You will need to define:
A) what environmental variable/condition change- Temperature and RH of ambient air, Q cooling, Q heating, …..
B) which variables can you control -recirculation rate, recirculation position, Total flow rate, TCC,…
C) which variable will you control - …..
D) how are you going to “move” between different operation schemes E) writhe “if - else” set of instruction for different controlled devices while
considering different operation scheme (see the example I gave you in class)
Absorption CycleSame as vapor compression but NO COMPRESSOR
Replace compressor
Absorption cooling cycleRelatively simple thermodynamics with addition of mixtures (water – ammonia)
HeatRich solution of
Rich solution of
H2O
H2O H2O + NH3
H2O + NH3
Mixtures(T-x diagram)
For P= 4 bar
Dew point curve
Bubble point curve
Saturated vapor
Saturated liquid
Mixture of liquid and vapor
Impact of Pressure
h-x diagram
Isotherms are showmen only in liquid region
hfg for H2O
hfg for NH3
Composition of h-x diagramSaturated vapor line at p1
Equilibrium construction line at p1
x1
A
Adding energy
B
Isotherm
at P 1 and T 1
Used to determine isotherm line in mixing region! Start from x1; move up to equilibrium construction line;move right to saturated vapor line; determine 1’; connect 1 and 1’.
X1’mass fraction of ammonia in saturated vapor
1e
h-x diagramat the end of your textbook you will find these diagrams
for 1) NH3-H2O
2) H2O-LiBr
LiBr is one of the major liquid descantsin air-conditioning systems
Adiabatic mixing in h-x diagram(Water – Ammonia)
From the textbook (Thermal Environmental Eng.; Kuehen et al)
Absorption cooling cycle
HeatRich solution of
Rich solution of
H2O
H2O H2O + NH3
H2O + NH3
Mixing of two streams with heat rejection (Absorber)
QHeat rejection
m1
m2
m3
xx3
1
2
3’
3
Mass and energy balance:
From mixture equation:
(1)
(2)
(3)
Substitute into (2)
Substitute into (3)
From adiabatic mixing (from previous slide)
m1
m2
m3
=pure NH3 (x2=1)
Mixture of 1 and 2cooling
mixture of H2O and NH3
Change of pressure(pump)
1
2
p1 ≠p2
p2
p1Saturated liquid at
Saturated liquid at
m1=m2
x1 =x2
x1=x2
1
2
Saturated liquid at p1
Sub cooled liquid at p2
Heat transfer with separation into liquid and vapor (Generator)
Apply mass and energy balance In the separator :
Defines points 3 and 4 in graph
Heat
Sub cooled liquid Saturated
liquid
Saturated vapor
We can “break” this generator into 2 units
Q12
m1=m2
m4
m3
Separator
Apply mass and energy balance In the heat exchanger
defines point 2in graph
Q12 /m1
x1
sub cooled liquid
mixture
=2V
2L=
heating
Heat rejection with separation into liquid and vapor (Condenser)
m1=m2
Saturated vapor
m1
m2
1
Saturated vapor at
p1
Saturated liquid at
p1
x1=x2
2x1 =x2
p1 =p2
Q1-2/m1
heat rejection
Throttling process (Expansion valve)
m1=m2
x1 =x2
p1 ≠p2
1
2
x1 =x2
p1 ≠p2
p1
p2
h1 =h21
2
Saturated liquid at
Saturated liquid at
T2
T1
2V
2L
Saturated vapor
Saturated liquid
Simple absorption system
3L
3V
3LLP
Saturated vapor at p2=p3=p4
Saturated liquid at p2=p3=p4
Saturated liquid at p1=p5=p6=p3_LLP
Simple absorption system
1
2
3
3V
3L 4 5
1’
5L
65V
3LLP
mixing
Useful cooling energy
Needed thermal energy
Heat transfer with separation into liquid and vapor (Generator)
Q12
=m2
m3
x1
mixture
=2V
2L=
heating
Q12
m1=m2
m4
m3
Separator
Q12 /m1
x1
sub cooled liquid
mixture
=2V
2L=
How to move point 4 to right ?
Heat rejection with separation into liquid and vapor (Enrichment NH3 in the vapor mixture)
Q12
m1=m2
m3
SeparatorQ12 /m1
x1
sub cooled liquid
mixture
4=2V
1cooling
2
2L
5
Q45 /m4
6=5V cooling
78m8x8
x8
This is our point
isothe
rm