https://docs.lib.purdue.edu/cgi/viewcontent.cgi?article=2875&context=iracc

High temperature heat pumps: Market overview, state of the art, research status, refrigerants, and application potentials

Abstract This study reviews the current state of the art and the current research activities of high temperature heat pumps (HTHPs) with heat sink temperatures in the range of 90 to 160 °C. The focus is on the analysis of the heat pump cycles and the suitable refrigerants. More than 20 HTHPs from 13 manufacturers have been identified on the market that are able to provide heat sink temperatures of at least 90 °C. Large application potentials have been recognized particularly in the food, paper, metal and chemical industries. The heating capacities range from about 20 kW to 20 MW. Most cycles are single-stage and differ primarily in the refrigerant (e.g. R245fa, R717, R744, R134a or R1234ze(E)) and compressor type used. The COPs range from 2.4 to 5.8 at a temperature lift of 95 to 40 K. Several research projects push the limits of the achievable COPs and heat sink temperatures to higher levels. COPs of about 5.7 to 6.5 (at 30 K lift) and 2.2 and 2.8 (70 K) are achieved at a sink temperature of 120 °C. The refrigerants investigated are mainly R1336mzz(Z), R718, R245fa, R1234ze(Z), R600, and R601. R1336mzz(Z) enables to achieve exceptionally high heat sink temperatures of up to 160 °C.

High Temperature Heat Pumps: Market Overview, Stateof the Art, Research Status, Refrigerants, and Application Potentials

A waste heat utilization device (2) for an internal combustion engine has a Rankine cycle (8) that recovers waste heat from an internal combustion engine (4), a generator (30) that is rotationally driven by an expander (14) and converts a rotational drive force into electric power, a converter (32) that controls the rotational speed of the expander (14) through the generator (30), refrigerant-condition detecting means (22, 24, 26, 28) that detects the pressure and temperature of a refrigerant passing through the expander (14), and a controller (34) that calculates pressure ratio Rp of the refrigerant in the immediate upstream and downstream of the expander (14) and specific heat ratio K of the refrigerant passing through the expander (14) on the basis of the pressure and temperature of the refrigerant, which have been detected by the refrigerant-condition detecting means (22, 24, 26, 28), calculates a preset pressure ratio Rps of the pressure ratio Rp by multiplying predetermined volume ratio Rv of the expander (14) by the specific heat ratio K, and specifies rotational speed N of the expander (14) to the converter (32) on the basis of the pressure ratio Rp and the preset pressure ratio Rps.

Waste Heat Utilization Device for Internal Combustion Engine

The waste heat recovery system includes a Rankine cycle device in which working fluid circulates through a pump, a boiler, an expander and then through a heat exchanging device, heat exchange occurs in the boiler between the working fluid and intake fluid that is introduced into an internal combustion engine while being cooled. The heat exchanging device includes a condenser condensing the working fluid, a receiver connected downstream of the condenser and storing liquid-phase working fluid, a subcooler connected downstream of the receiver and subcooling the liquid-phase working fluid, and a selector device serving to change the ratio of the condenser to the subcooler. The waste heat recovery system further includes a determination device for determining required cooling load for the intake fluid, and a controller for controlling the selector device depending on the required cooling load determined by the determination device.

Waste heat recovery system

A method and system for operating a cascaded organic Rankine cycle (ORC) system (100) utilizes two waste heat sources from a positive-displacement engine (106), resulting in increased efficiency of the engine (106) and the cascaded ORC system (100). A high temperature waste heat source from the positive-displacement engine (106) is used in a first ORC system (102) to vaporize a first working fluid (118). A low temperature waste heat source from the positive-displacement engine (106) is used in a second ORC system (104) to heat a second working fluid (130) to a temperature less than the vaporization temperature. The second working fluid (130) is then vaporized using heat from the first working fluid (118). In an exemplary embodiment, the positive-displacement engine (106) is a reciprocating engine. The high temperature waste heat source may be exhaust gas and the low temperature waste heat source may be jacket cooling water.

Cascaded organic rankine cycle (orc) system using waste heat from a reciprocating engine

The shaft (20) of an engine (19) is coupled to a turbine (28) of an organic Rankine cycle subsystem which extracts heat (45-48, 25) from engine intake air, coolant, oil, EGR and exhaust. Bypass valves (92, 94, 96, 99) control engine temperatures. Turbine pressure drop is controlled via a bypass valve (82) or a mass flow control valve (113). A refrigeration subsystem having a compressor (107) coupled to the engine shaft uses its evaporator (45a) to cool engine intake air. The ORC evaporator (25a) may comprise a muffler including pressure pulse reducing fins (121, 122), some of which have NOx and/or particulate reducing catalysts thereon.

Organic rankine cycle mechanically and thermally coupled to an engine driving a common load

A pair of organic Rankine cycle systems (20, 25) are combined and their respective organic working fluids are chosen such that the organic working fluid of the first organic Rankine cycle is condensed at a condensation temperature that is well above the boiling point of the organic working fluid of the second organic Rankine style system, and a single common heat exchanger (23) is used for both the condenser of the first organic Rankine cycle system and the evaporator of the second organic Rankine cycle system. A preferred organic working fluid of the first system is toluene and that of the second organic working fluid is R245fa.

Cascaded organic rankine cycles for waste heat utilization

In order to effectively extract the waste heat from a reciprocating engine (11), the normal heat exchanger components of an engine are replaced with one or more heat exchangers (14, 16) which have the motive fluid of an organic rankine cycle system flowing therethrough. With the heat transfer in the plurality of heat exchangers, the engine is maintained at a reasonable cool temperature and the extracted heat is supplied to an ORC turbine (21) to generate power. The heat is derived from a plurality of sources within the reciprocating engine, and at least two of those sources have their fluids passing through the same heat exchanger. In one embodiment, the engine coolant and the engine lubricant pass through the heat exchanger in the same direction, and the ORC motive fluid passes therethrough in a counterflow relationship.

Organic rankine cycle system with shared heat exchanger for use with a reciprocating engine

A power conversion system which uses a plurality of transistors to convert DC power to AC power is made more efficient by the use of liquid refrigerant to cool the transistors. A plurality of passages are formed in a cold plate on which the transistors are mounted, and liquid refrigerant is flashed into the passages to cool the cold plate and the transistors. The liquid refrigerant can by derived from a condenser from an organic rankine cycle or a vapor compression cycle.

Power converter cooling

Ketone C6F, which has the chemical formula: CF3CF2C(O)CF(CF3)2, has been introduced recently as a zero-ODP, zero-GWP fire extinguishing fluid. Its non-flammability and non-toxicity combined with its excellent environmental properties make it an attractive fluid for HVAC applications. Its low density limits its use to centrifugal water-cooled chiller applications. The relatively high critical temperature of the fluid promises good thermal cycle efficiency. However, the slope of the saturation dome on the temperatureentropy diagram forces the use of a vapor suction / condensed liquid heat exchanger to prevent wet compression and reduce the throttling losses. The low speed of sound of the fluid allows direct drive single stage compressor operation at relatively small tonnages. The sub-atmospheric evaporator (0.162 bar) and condenser (0.604 bar) pressures necessitate the use of a purge but eliminate the need for pressure vessel code certification.

/pdf/cycle-analysis-and-turbo-compressor-sizing-with-ketone-c6f-22mnud97o3.pdf

Bruce P. Biederman

Papers

Organic rankine cycle mechanically and thermally coupled to an engine driving a common load

Cascaded organic rankine cycles for waste heat utilization

Organic rankine cycle system with shared heat exchanger for use with a reciprocating engine

Power converter cooling

Cycle analysis and turbo compressor sizing with ketone c6f as working fluid for water-cooled chiller applications