Vapour Jet Refrigerator / Heat Pump R853

Transcription

1 Vapour Jet Refrigerator / Heat Pump R853 Enables demonstration and investigation of the combined Rankine and Vapour Compression Cycle Is an example of a refrigerator or heat pump driven by a Heat Input as opposed to the more usual work input Uses hot water as the high grade heat source, thus limiting the maximum temperature to 100 o C Evaporation and Condensation may clearly be seen through glass cylinders As a heat pump, the unit shows approximately the same primary energy ratio as a work-driven heat pump All important components are mounted on the front panel and quickly responds to a change in operating conditions. Optional Solar Panels available Two Year Warranty Page 1 of 5

2 Introduction Refrigerators and Heat Pumps are machines which extract heat from a low temperature region and reject heat to a region at a higher temperature. If the prime function of the machine is to extract heat from low temperature region, the machine is a REFRIGERATOR. Conversely, if the prime function is to deliver heat at a useful temperature, the machine is a HEAT PUMP. The Laws of Thermodynamics indicate that the transfer of heat from a cold to a hot body is impossible without the aid of external assistance, i.e. a high grade energy input. This input can be in the form of a WORK TRANSFER or of a HEAT TRANSFER AT A HIGH TEMPERATURE. Since work is the most valuable form of energy, the quantity of work required for a given heat transfer from a cold to a hot body, will be less than if a high grade heat input is employed. However, work is usually derived from a very high grade heat input in a Thermal Power Station or other Prime-Mover. As the thermal efficiency of these is usually between 25 and 35% there can be an overall advantage in using a heat input to drive a heat pump or refrigerator. The Combined Rankine and Vapour Compression Cycle. The pressing need to conserve fossil fuels has aroused interest in two distinct possibilities associated with refrigeration: a) Refrigerators which will operate from non-fuel consuming input (e.g. solar radiation, waste heat, geothermal heat). b) Combined prime movers and heat pumps which burn fuels, but which make more heat available for intermediate grade heating purposes than was available from the fuel consumed. The Combined Rankine and Vapour Compression Cycle makes both of these possible. In a Combined Rankine and Vapour Compression Cycle, a high grade heat input generates high pressure vapour in a boiler. This vapour expands in a turbine producing work, and then passes into a condenser where it is liquified by rejecting heat. The liquid is then pumped back into the boiler for re-evaporation. The work produced by the turbine drives a conventional vapour compression cycle refrigerator or heat pump. Assuming that the same fluid is used throughout, the turbine and compressor can discharge into a common condenser. Neglecting heat losses, it will be seen that the ratio Intermediate Grade Heat Delivered = Q H + Q L is greater than unity Q High Grade Heat Input H The effectiveness of the combined Rankine and Vapour Compression Cycle depends upon the temperatures at which, i. heat is supplied at the boiler, ii. heat is available to the evaporator, iii. heat is rejected at the condenser, iv. The efficiency of the expansion and compression processes. The unit will be a valuable teaching aid for students of: Refrigeration & Air Conditioning Building Services Mechanical Engineering Plant and Process Engineering Energy Conservation Energy Management Chemical Engineering Food Technology Marine Engineering Agriculture Engineering Page 2 of 5

3 Experimental Capabilities The following experiments can be performed: Analysis of the combined Rankine and Vapour Compression Cycle. Demonstration of the characteristics of an ejector or thermo compressor. Production of performance curves as a refrigerator and comparison with ideal o Rankine/Vapour Compression cycle. Production of performance curves as a heat pump and comparison with ideal o Rankine/Vapour Compression Cycle. Investigation of entrainment mass ratio at various pressures. Demonstration of adiabatic mixing of hot and cold vapour. Demonstration of adiabatic throttling. Description The unit may be regarded as a combined heat engine and a refrigerator/heat pump. The system powering the refrigerator/heat pump works on the well-known Rankine cycle (frequently used in steam power plants.) In this cycle the unit takes in heat at a very modest temperature (about 90 o C) and rejects heat at the condenser temperature (about 30 o C). The work output of this engine is in the form of the kinetic energy of a jet instead of shaft work as is normal with a Rankine cycle. The refrigerator/heat pump operates on the Vapour Compression Cycle and uses the output of the Rankine Cycle (i.e. the kinetic energy of the jet). It takes in heat at a low temperature in an evaporator and rejects heat at a higher temperature using the same condenser as the engine. Both the Rankine Power Plant Cycle and the Vapour Compression/Heat Pump Cycle are included in most courses of study for young engineers. The Hilton Vapour Jet Refrigerator/Heat Pump R853 demonstrates practically, the potential of combining these cycles so that a heat pump or refrigerator can be run from a heat output. Controls and operation The unit has three simple controls: 1. Condenser cooling water flow rate this, in conjunction with the inlet temperature of the cooling water, determines the temperature and pressure in the condenser, and thus the temperature at which heat is rejected. 2. A variable transformer this varies the heat input to the electric heater in the evaporator, which in turn controls the evaporation temperature. A voltmeter and ammeter indicates the energy input to the heater. 3. A manually adjustable throttle valve this is placed between the vapour generator and the nozzle and enables the unit to be operated below the maximum pressure. Instrumentation is provided for temperature and pressure measurement, the heat input to the evaporator and the water flow rate. The mass flow rates of the refrigerant at the evaporator can be readily obtained from the measured energy transfer rates and the enthalpy changes. The heat transfer at the refrigerant vapour generator is obtained by the difference between the heat transfer at the condenser and that at the evaporator and the heat transfer rate to or from the surroundings. It should be noted that the performance of all vapour power plants, refrigerators and heat pumps falls as the condenser temperature rises. This is true of the Vapour Jet Refrigerator/Heat Pump and it is recommended that, if a useful range of test conditions is to be investigated, the condenser cooling water temperature should not exceed 22 o C. Page 3 of 5

4 Optional Solar Panels and Installation Package F821S The R853 Vapour Jet Refrigerator/Heat Pump may be run from any source of hot water at a sufficiently high temperature, i.e. about 90 o C. In locations where conditions are suitable, the F821S Solar Panels & Installation Kit enables these units to be run from hot water generated in solar panels. The kit, which is for on-site assembly and installation, includes the solar panels and all the components required for connection to the unions provided on these units. Specification Panel: High quality glass reinforced plastic on which the following are mounted: Steam Generator: Rectangular glass reinforced plastic insulated vessel fitted with 1.5kW immersion heater and containing the refrigerant vapour generator. Refrigerant Vapour Generator: Cylindrical stainless steel shell, 75mm dia x 200mm long, with dished ends fitted with sight glass and pre-heating coil. Ejector Nozzle: Convergent-divergent, throat diameter 1.7mm. Compressor: Diffuser: With combining cone, parallel and divergent portions. Evaporator: Thick walled glass cylinder fitted with metal end plates and P.T.F.E seals. Evaporator incorporating a 500W heater controlled by a variable transformer and a float type expansion valve. Condenser: Thick walled glass cylinder fitted with water cooling coil. Surface area of coil: 0.1m 2. Feed Pump: Reciprocating plunger type pump fitted with P.T.F.E. seals and water jacket, driven by electric motor through worm reduction gearbox to give approximately 60 double strokes / minute. Instrumentation Thermometer: Digital type K electronic thermometer with 0.1 o C resolution and 12 way selector connected to 9 thermocouples to measure all important temperatures. Pressure Gauges: Two 0 to 800 knm-2 to indicate refrigerant vapour generator and nozzle inlet pressure. Two 100 to knm-2 to indicate evaporator and condenser pressure. Flow Meter: Variable area glass tube type fitted with control valve to measure water flow rate through condenser. Range 0 to 75g s -1. Voltmeter and Ammeter: To measure power input to evaporator. Ranges 0 to 250Vand 0 to 3A respectively. Safety features Pressure Relief Valves: Fitted to vapour generator, evaporator and condenser. High Pressure Cut Out Fitted to vapour generator and condenser. Switches: Low Water Flow Switch: To switch off power supply if insufficient water flows through the condenser. Solenoid Valve: To isolate vapour generator from ejector, evaporator and condenser. High Temperature Cut Out: Fitted to all heater elements. All circuits are protected by a fuse. Dimensions Height: 92.5cm Depth: 43.0cm Width: 106cm Weight: 102kg Accessories and Spares Unit supplied with: One experimental operating and maintenance manual in English, Spanish or French. Accessories and spares for 2 years normal operation. List available on request. Throttle Valve: Manually adjustable to vary nozzle inlet pressure. Page 4 of 5

5 Services Required Electrical: A: 2.5kW, Volts Single Phase 50Hz(With earth/ground). B: 2.5kW, Volts Single Phase, 60Hz (With earth/ground). Water: 250 litres / hour at 15m head. Water temperature should not exceed 22 o C if a useful range of test conditions are to be investigated. Ordering Information Order as : R853 Vapour Jet Refrigeration/Heat Pump Optional: F821S Solar Panels and Installation Package Language Either: English, Spanish or French. Shipping Specifications Net Weight: 102kg. (approx.) Gross Weight: 190kg. (approx.) Packing Case Dim: 1.25 x x 1.194m (approx) Packing Case Volume: 0.928m3 (approx.) Also Available On Request Further detailed specification. Additional copies of instruction manual. Recommended list of spares for 5 years operation. Suitable chiller details. Optional F821S Solar Panels and Installation Kit The solar panels are of the flat plate type with a selective finish, housed in a durable aluminum casing. The rear face of the panel is well insulated with rockwool and the front face is protected by an air gap and a special plastic film having a higher transmission than glass. To reduce heat losses and wind loads, the panels should be mounted in a sunny sheltered position so that, at noon, the face of the panel receives solar radiation normally. The panels should be as close as possible to the connected unit (12m maximum) and if possible at a higher level to assist venting. Screens are provided on the panels and these must be closed when the panels are not in use. Water connections between the panels and unit are via annealed copper tubes which are insulated during assembly. The water is pressurized to 200kN m -2 g by a pressurised air cushion in an expansion vessel and an automatic vent discharges air from the highest point. A water meter and thermocouples (for connection to the unit instrument panel) enable the heat collection rate to be measured. P.A.HILTON Ltd. Horsebridge Mill, King s Somborne, Stockbridge, Hampshire, SO20 6PX, England. Telephone: National (01794) International Fax: National (01794) International Website: sales@p-a-hilton.co.uk Page 5 of 5