Lecture Objectives: Learn about Start energy production systems Desiccant systems Start energy production systems - Sorption cooling

Desiccant Systems: Reading assignment http://www.ce.utexas.edu/prof/Novoselac/classes/CE397b/Handouts/1-s2.0-S1364032109001737-main.pdf

Desiccant wheel

Desiccant wheel Figure 3 – A desiccant-based cooling system combined with regenerative heat exchanger, vapor compression cooling, and evaporative humidifier (hybrid system).

Variation in Cycles Much more in the paper I gave you (Technical development of rotary desiccant dehumidification and air conditioning)

Absorption Cycle Same as vapor compression but NO COMPRESSOR Replace compressor

Absorption cooling cycle Rich solution of Heat H2O H2O + NH3 Rich solution of H2O H2O + NH3

Mixtures (T-x diagram) Dew point curve Saturated vapor Mixture of liquid and vapor Saturated liquid Bubble point curve For P= 4 bar

h-x diagram hfg hfg Isotherms are shown only in liquid region for H2O for NH3 Isotherms are shown only in liquid region

Composition of h-x diagram Saturated vapor line at p1 Equilibrium construction line at p1 1e 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’. Isotherm at P1 and T1 Adding energy B A x1 X1’ mass fraction of ammonia in saturated vapor

h-x diagram at the end of your textbook you will find these diagrams for 1) NH3-H2O 2) H2O-LiBr LiBr is one of the major liquid descants in air-conditioning systems

Adiabatic mixing in h-x diagram (Water – Ammonia) From the textbook (Thermal Environmental Eng.; Kuehen et al)

Absorption cooling cycle Rich solution of Heat H2O H2O + NH3 Rich solution of H2O H2O + NH3

Mixing of two streams with heat rejection (Absorber) mixture of H2O and NH3 m2 m3 =pure NH3 (x2=1) m1 m3 m2 m1 2 Q cooling Heat rejection Mixture of 1 and 2 3’ Mass and energy balance: (1) (2) 1 3 (3) x3 x From mixture equation: Substitute into (2) Substitute into (3) From adiabatic mixing (from previous slide)

Simple absorption system 3V 3L 3LLP

Simple absorption system Saturated vapor at p2=p3=p4 3V 6 3 5V mixing 1’ Needed thermal energy Useful cooling energy 3L 4 3LLP 5 2 Saturated liquid at p2=p3=p4 1 5L Saturated liquid at p1=p5=p6=p3_LLP

Heat transfer with separation into liquid and vapor (Generator) How to move point 4 to right ? =2V =2V heating m4 Q12 /m1 2L= 2L= =m2 m1 =m2 mixture Separator sub cooled liquid mixture x1 x1 Q12 m3 Q12 m3

Heat rejection with separation into liquid and vapor (Enrichment NH3 in the vapor mixture) This is our point cooling 1 4=2V Separator 6=5V Q12 /m1 cooling Q45 /m4 x8 m8 8 7 m1 =m2 5 2 sub cooled liquid mixture isotherm m3 2L Q12 x1 x8

Simple absorption system Generator with of Enrichment NH3 Different 8V 9 8L 10 8LLP 11

Absorption system with Saturated vapor at p2=p3=p4 3V 8V 3 mixing 11 8L 1’ Useful cooling energy 8LLP 10 3L 2 9 Saturated liquid at p2=p3=p4 1 Saturated liquid at p1=p5=p6=p3_LLP

More detailed absorption cooling Refrigeration and air conditioning (Ramesh et al)