1. Reversed cycle machines
Dr. Tamás Szakács
college senior lecturer
University of Óbuda
Budapest Bécsi út 96/B
H-1034 Budapest, Hungary

2. Content of the presentation
Introduction
Reverse cycle machines
Design of the inner cycle
Design of the heating/cooling properties
Examples

3. Introduction Reversed cycle machines
Machine is producing work from introduced heat. E.g. the idealized Carnot cycle, or the realized Otto, Diesel or Joule cycles.
Reversed cycle transforms heat opposite the natural direction, but requires work. For example: Refrigerator, heat-pump.

4. Introduction Importance of reversed machines
Increasing energy consumption of EU countries.
Peak-loads in summer (originated from air conditioning).
Reversed machines can help reducing energy consumprion even in increasing demands.

5. Reversed cycle machines
Coolong (refrigerating)
Air-conditioning
Heating
Drying

6. Heating by reverse cycle air conditioning
Reverse cycle air conditioning extracts heat from a natural heat source (e.g. soil, or the outside air, even on mid-winter nights) and transfers it inside. A refrigerant is passed through an external coil, absorbing the heat. This refrigerant is then compressed by a compressor into a fan coil unit (or ‘condenser’) inside the home, releasing its heat into the room.

7. Heating by reverse cycle air conditioning
Advantages:
One of the most economical forms of heating
Able to provide both heating and cooling
Have no exposed elements or flames
Lifetime of up to 20 years
Filter and dehumidify air
Can utilize district- and waste heat, heat from COG, and renewable heat sources.

8. Reverse cycle air conditioning
Types:
Portable
Window/wall units
Split systems
Multi-split systems
Ducted systems
Reverse_cycle_AC.pdf

9. Mollier diagram with approximation range and rated refrigeration cycle
AMMONIA REFRIGERATION CYCLE_p639_final.pdf
Mollier diagram with approximation range and rated refrigeration cycle

12. Solar assisted air conditioning

13. 7_Holter_Anlagenkonzepte.pdf

14. Principle of an absorption chiller
D23-solar-assisted-cooling.pdf
Principle of an absorption chiller
Key Issues for Renewable Heat in Europe (K4RES-H)
Solar Assisted Cooling – WP3, Task 3.5 Contract EIE/04/204/S

15. Principle of an absorption chiller
Keep Cool
Solar Cooling
Published and produced by: Österreichische Energieagentur – Austrian Energy Agency
Otto-Bauer-Gasse 6, A-1060 Vienna, Phone +43 (1) , Fax +43 (1)
Internet:
Principle of an absorption chiller

16. Principle of an absorption chiller
Keep Cool
Solar Cooling
Published and produced by: Österreichische Energieagentur – Austrian Energy Agency
Otto-Bauer-Gasse 6, A-1060 Vienna, Phone +43 (1) , Fax +43 (1)
Internet:
Principle of an absorption chiller

17. Principle of an adsorption chiller
Key Issues for Renewable Heat in Europe (K4RES-H)
Solar Assisted Cooling – WP3, Task 3.5 Contract EIE/04/204/S

18. Principle of an adsorption chiller
Published and produced by: Österreichische Energieagentur – Austrian Energy Agency
Otto-Bauer-Gasse 6, A-1060 Vienna, Phone +43 (1) , Fax +43 (1)
Internet:
Principle of an adsorption chiller

19. Solid desiccant cooling with rotating wheels
Published and produced by: Österreichische Energieagentur – Austrian Energy Agency Otto-Bauer-Gasse 6, A-1060 Vienna, Phone +43 (1) , Fax +43 (1)
Internet:
The DEC-process can be summarised as follows:
1 -> 2 sorptive dehumidification of supply air; the process is almost adiabatic and the air is heated by the adsorption heat and the warmed wheel matrix coming from the regeneration side
2 -> 3 pre-cooling of the supply air in counter-flow to the return air from the building
3 -> 4 evaporative cooling of the supply air to the desired supply air humidity by means of a humidifier
4 -> 5 supply air temperature and humidity are increased due to internal and external loads
5 -> 6 return air from the building is cooled using evaporative cooling close to the saturation
6 -> 7 the return air is pre-heated in counter-flow to the supply air by means of a highly efficient air-to-air heat exchanger, e.g. a heat recovery wheel
7 -> 8 regeneration heat is supplied by a heating coil; this heating coil is driven by hot water; for instance by hot water generated by solar thermal collectors
8 -> 9 regeneration process of the desiccant material; the water bound in the pores of the desiccant material of the sorption wheel is desorbed by means of regeneration air
Solid desiccant cooling with rotating wheels

20. Published and produced by: Österreichische Energieagentur – Austrian Energy Agency Otto-Bauer-Gasse 6, A-1060 Vienna, Phone +43 (1) , Fax +43 (1)
Internet:
The DEC-process can be summarised as follows:
1 -> 2 sorptive dehumidification of supply air; the process is almost adiabatic and the air is heated by the adsorption heat and the warmed wheel matrix coming from the regeneration side
2 -> 3 pre-cooling of the supply air in counter-flow to the return air from the building
3 -> 4 evaporative cooling of the supply air to the desired supply air humidity by means of a humidifier
4 -> 5 supply air temperature and humidity are increased due to internal and external loads
5 -> 6 return air from the building is cooled using evaporative cooling close to the saturation
6 -> 7 the return air is pre-heated in counter-flow to the supply air by means of a highly efficient air-to-air heat exchanger, e.g. a heat recovery wheel
7 -> 8 regeneration heat is supplied by a heating coil; this heating coil is driven by hot water; for instance by hot water generated by solar thermal collectors
8 -> 9 regeneration process of the desiccant material; the water bound in the pores of the desiccant material of the sorption wheel is desorbed by means of regeneration air

21. Solid desiccant cooling with rotating wheels
Warm and humid ambient air enters the slowly rotating desiccant wheel and is dehumidified by adsorption of water (1-2). Since the air is heated up by the adsorption heat, a heat recovery wheel is passed (2-3), resulting in a significant precooling of the supply air stream. Subsequently, the air is humidified and further cooled by a controlled humidifier (3-4), according to the desired temperature and humidity of the supply air stream. The exhaust air stream of the rooms is humidified (6-7) close to the saturation point to exploit the full cooling potential in order to allow an effective heat recovery (7-8). Finally, the sorption wheel has to be regenerated (9-10) by applying heat in a comparatively low temperature range from 50°C-75°C, to allow a continuous operation of the dehumidification process.
B: Heating case
In periods of low heating demand, heat recovery from the exhaust air stream and enthalpy exchange by using a fast rotating mode of the desiccant wheel may be sufficient. In cases of increased heating demand, heat from the solar thermal collectors and, if necessary, from a backup heat source (4-5) is applied.
Flat plate solar thermal collectors can be applied normally as a heating system in solar assisted desiccant cooling systems. The solar system may consist of collectors using water as fluid and a hot water storage, to increase the utilisation of the solar system. This configuration requires an additional water/air heat exchanger, to connect the solar system to the air system. An alternative solution, leading to lower investment cost, is the direct supply of regeneration heat by means of solar air collectors.
D23-solar-assisted-cooling.pdf
Solid desiccant cooling with rotating wheels
Key Issues for Renewable Heat in Europe (K4RES-H)
Solar Assisted Cooling – WP3, Task 3.5 Contract EIE/04/204/S

22. Overview of the most common solar assisted air conditioning technologies

23. Overview of the most common solar assisted air conditioning technologies

24. Mollier h-x-Diagramm für feuchte Luft für p=1 bar

27. Idealized Carnot cycles
Ambient temperature S S S S
Single purpose heat-pump
Multipurpose heat-pump
Electric powerplant
Cooler

28. Calculation example Example 1
How much is the cooling capacity of a cooler made of an adiabatic compression and expansion pistion cycle with ammonia refrigerant?
The temperature of the condensation is 30C, the evaporation -10C degrees. The compressor is supplied with dry saturated gas. (x2=1). The condensation is performed till x3= 0.

29. 3 2
275
240
1542
1355 4 1

31. Transferred heat in the evaporator by 1 kg cooling agent:
Mass flow of the circulated cooling agent:
Work required to power the compressor:
Work done by the expansion piston

32. Work required to keep the cycle up:
COP:
Supplied volume flow of the compressor:

33. Calculation example Example 2
The temperature of a m=18000kg air t1=80°C, moisture content x1=0,03kg/kg. Make a x4 = 0,01 kg/kg dry air by cooling, while keep the outlet temperature same as t1. How much water has to be drained? How much heat has to be subtracted for the cooling and added for the re-heating?

34. Properties of point 1
t1 = 80 oC
h1 = 160 kJ/kg
x1 = 0,03 kg/kg.
Properties of point 2
t2 = 14 oC
h2 = 141 kJ/kg
x2 = x1
Properties of point 3
t3 = t2 = 14 oC
h3 = 39 kJ/kg
x3 = 0,01
 = 1

35. Properties of point 4
t4 = t1 = 80 oC
h4 = 108 kJ/kg
x4 = x3 = 0,01 kg/kg.
Water removed
Heat removed by cooling
Heat added by re-warming

36. Thank you for the attention