New Sensor Technologies Control phase of Refrigerant, made Ammonia more Safe and Optimizing all type of Refrigeration systems, work with NH3, CO2, Propan, HFC/HFO Refrigerant Information, experiences and Validation of the HB-Products Vapor/gas Quality sensor Bachelor thesis by Oliver Kacic, -Nr.: 46032, Hochschule Karlsruhe Next generation of HBX Vapor Quality sensors with both integrated sensor, evaporator-control and remote-control feature are now ready to optimize all types of evaporators Optimization of key processes in a refrigeration system For maximum cooling load there was an EER increase of 18,6% (EER = Energy efficiency Ratio). Low Carbon Technologies Patent No.: US 9,587,866 B2 Validation of vapor oqality sensor 01 13-04-2018 page 1
Theory measuring principle The sensor is based on the capacitive measurement principle in which two or more measuring electrodes/ conductors measures the charge and change in electrical field/resistance depending on difference in the dielectric properties of various media. Hereby the ratio between vapor and liquid amounts is measured instantaneously, i.e., without delay as a volume based Void Fraction measurement. What is an electrical capacitor? A capacitor is a component designed to create and hold an electric field, which means that capacitors can store energy. It takes energy to pull electric charges apart and to establish an electric field between the separated conductors. Here is Q the charge stored at a given potential voltage difference: Thermodynamics: Parameters which influence the flow pattern and have strong impact on heat transfer: The volumetric Void Fraction is defined as the ratio of the volume occupied by the liquid in the tube and the total volume of the tube. It can thus be seen as an average of the cross sectional Void Fraction over the tube. For vapor qualities above 0.5, there is approximately a linear link to the Void Fraction as shown in the Figure. Void fraction vs. vapor quality In thermodynamics, Vapor Quality is the mass fraction between vapor and liquid in a saturated wet mixture; i.e. dry vapor has a quality of 1.0, and pure liquid has a quality of 0. Quality X can be calculated by dividing the mass of the vapor by the mass of the total mixture. Low Charge Ammonia DX Systems with Zero Superheat Validation of vapor oqality sensor 01 13-04-2018 page 2
Facts Experience in testing and installation on primary Ammonia systems have proven that a Vapor Quality Sensor mounted in the outlet of an evaporator optimizes the entire system and makes it possible to control and limit the amount of refrigerant in the system under all conditions (including part load operation). The sensor measures Vapor Quality as the ratio of the vapor and liquid in a two-phase flow as a volumetric Void Fraction measurement. Liquid feed/control on plate heat exchanger is often associated with challenges to control the capacity of a plate heat exchanger since calculations and design are based on 100% load. By measuring the vapor quality with an "X" sensor, it is now possible to optimize the refrigerant supply to match the load. Experience from several installations show that Vapor Quality Control is a superior principle for both flooded and DX systems, with significant impact on the overall heat exchanger performance. Sensor mounted in the outlet of a DX Air-Cooler in Australia A statement from the world's leading Low Charge Ammonia company Scantec in Australia: Using electronically controlled refrigerant injection based on refrigerant quality at evaporator exit optimize evaporator performances: X-Sensor Positive superheat for 0.95 < x < 0.99 X (quality based) control more stable than superheat based Holding freezer temperature at -22 C for - 27.9 C SST A statement from the world's leading heat exchanger company Alfa Laval: To obtain optimum heat transfer adopt a Vapor Quality Sensor in the outlet. Optimum circulations rate (flooded) X 0.7 to 0.85...CR 1.2 to 1.4 Validation of vapor oqality sensor 01 13-04-2018 page 3
Bachelor thesis by Oliver Kacic Validation of the HB-Products gas quality sensor as well as an efficiency analysis of a directevaporation R717 refrigeration system with gas quality sensor in comparison to superheat control. Vapor Quality Superheat Energy Efficiency Ratio, 14 C evaporation tempeature, control variables of X = 98 % and Toh = 1,5 K, load 100%. For maximum cooling load there was a EER increase of 18,6 % possible (EER = Energy efficiency Ratio). It was confirmed that a direct-evaporating ammonia refrigeration plant can be operated in a stable state by the gas quality sensor. It was also shown that an efficiency increase of up to 18.6 % is possible due to the gas quality control, with an X-value of 98 %, against an overheating control with 1.5 K. It was also found that the gas quality control depends on the flow regime in the plate evaporator. Consequently, this excludes smaller performance ranges for gas quality control. With regard to the flow types and control in the partial load range, further research is required for the operation of the gas quality sensor. Comment: conclusion from his testing was that the benefit of controlling with the HBX-DX vapor quality sensor is only present at max load, at part load and very low load, they have not been able to get the system working optimal. I had an expectation that it`s possible to optimize the control by changing set point for the dryness "X" by incrementally increased the settings from X 0.98 to 1.0 (starving the evaporator), at 0.99 the regulation works fine where the system was in balance when the evaporator load was change from 100 to 50%. The vapor quality was homogeny with strong relation between the sensor signal and valve operation/position. Conclusion: It is a great advantage to apply a Vapor Quality Sensor for controlling plate heat exchangers. Both DX and flooded systems can be advantageously controlled very accurately with homogeneous vapor quality and very small pressure variations as a consequence. Further, it is proved that it`s possible to optimize the evaporator performance during part load operation by minimizing the refrigerant charge (starve the evaporator). Validation of vapor oqality sensor 01 13-04-2018 page 4
Low Charge Ammonia DX Systems with Zero Superheat The desire to use the world s most energy-efficient refrigerant, ammonia, in dry expansion refrigeration systems has led to many challenges and has rightfully earned the reputation of being a poor solution that does not always work well. Many attempts have been made without any significant breakthroughs. It was necessary to compromise from the normal DX design and install liquid separators before the compressors and set superheating very high in order to avoid liquid flood-back and potential compressor damage. High superheating, and inefficient/non-dynamic evaporators with not equal liquid distribution combined with ammonia s high latent heat of vaporization have caused most of the challenges. Altogether, this has led to very poor energy efficiency. It is also a fact that water in the ammonia changes the boiling point and thus the calculated superheat values; 1% water in the ammonia increases the boiling point by around 5K towards the end of the evaporation process (Nelson, 2010), this phenomenon will act as a false superheat signal and react accordingly. Our recommendation for optimal and safe operation in combination with Vapor Quality Control for low temperature NH3 DX evaporators is to use liquid distribution works by gravity, designed as small tanks/pots without pressure drop as Küba CAL and Colmac Coil tank distributor. Experience gathered from four ammonia DX systems operating in Australia shows that the systems with HBX-DX Vapor Quality measurement/control are more energy efficient and do not result in pressure variations of the same magnitude as DX systems based on superheat controlled refrigerant injection. Example of tank liquid distributors: Colmac-Coil tank distributor Validation of vapor oqality sensor 01 13-04-2018 page 5
Graphics display of the Control pattern Typically control pattern for P-control with time-based valve-opening and closing-time 0.8 wet sensor Vapor Quality X Sensor dry out time after defrost and start up with ramp function for safe valve operation (only in function when using the Run-In signal, pin.5) Valve opening time Time: 0.1%/sec. Approx 12minute Low limit safety Alarm at X 0.90 Closing the liquid Valve to minimum Valve opening immediately Valve Opening 100% Wet sensor X Vapor Valve closing time Time: 0.3%/sec. 5.5minute 80% 60% 40% Alarm...0.90 Set.pkt...0.97 +5 K 1.0 Dry sensor Time 20% Min. Valve opening Control pattern with Sensor dry out time during start up and after defrost, dry out time is adjustable with ramp function for safe opening of the liquid valve. (control of the valve opening time) The sensor has built-in advanced control where it is possible to control all types of evaporators, expansion valve open and close times can be varied fro 0.1 to 10% / sec., Start-up with ramp function and sensor drying ensure secure startup, low limit safety alarm closing the liquid valve to minimum opening. External start and stop function from a master control system is required when the sensor is used for control. NOTE: During start up or after defrost there are liquid droplets on the sensor part from condensated vapor. These droplets will effect the sensor and give a high ma output. Alarm could also be activated, if the alarm delay is too short. This phenomenon should be managed during start up. We recommend to dry out the sensor during start up by opening the liquid valve in xx sec. and adding refrigerant to the evaporator, This will ensure that the vaporized gas will dry the sensor before starting to control from dry sensor (zero signal 4mA +0.5). Increase of pressure will also condense some of the refrigerant vapor which then will become more wet and thereby affects the sensor briefly until the system is in balance. The minimum opening of the expansion valve ensures that there is always a small load of the evaporator, the opening must be limit to ensure that all refrigerant is evaporated with fans/ventilators running minimum speed and with maximum ice build-up on the evaporator surface. Validation of vapor oqality sensor 01 13-04-2018 page 6
HBX-XX Sensors with integrated Control function In Control mode, you can optimize all required control parameters as shown in the diagram. It is especially important to start and stop the control function with the digital input on pin.5 (Run-In signal) to close the expansion valve at stop and defrost. Use Run-IN signal for Start/Stop command (Shut-off) and defrost. Sensor dry out and ramp startup are only active when using the Run-In signal. Sensor dry out time after defrost and start up with ramp function for safe valve operation. (only enabled with Run-In function set to ON) Low limit safety Alarm Closing the liquid Valve immediately to minimum valve opening. Controlling the evaporator capacity: The expansion valve opens as a function of a deviation from the desired set-value, the opening degree depends on the amplification (P-band) and opening / closing times for the expansion valve. Eksample, Set-value X on 0.98, P-band on 50% 20mA 12mA Control Output P-band With to small P-band it will act more or les as ON / OFF control where the control valve hunting. Output at X 0.99 is (100-P-band)x(100-99) = 50% (12mA) P-band in % X value as integer 4mA 0.98 0.99 100 X Dryness/Superheat We recommend that set point not should be set lower than "X" 0.97 Dryness versus Superheating range is 0.97 = +1 K +/-1, 0.98 = +2 K +/- 1, 0.99 = +3 K +/-1 Validation of vapor oqality sensor 01 13-04-2018 page 7
Connection diagram for HBX/C (4-20mA motor valve). New mk2 generation of HBX Vapor Quality sensors with integrated sensor, evaporator-control and remote-control feature. New opportunities when used as controller: Both sensor and Control output, analog 2 x 4-20mA. Addinational analog sensor output showing Vapor Quality, 4-20mA (with Valve Cable. Pin 4). Remote setting or temperature compensation, analog 4-20mA input (pin. 3). Sensor output 3 can be changed to a digital relay output opening and closing a solenoid valve (used to control the draining of condensate during defrost or closing a liquid solenoid valve). Validation of vapor oqality sensor 01 13-04-2018 page 8
Connection diagram for HBX/S (stepper motor). Advanced settings: Stepper motor settings should be set according to the type of valve. Carel E2V Validation of vapor oqality sensor 01 13-04-2018 page 9
Connection diagram for HBX/PWM (puls modulation valve). HBX-DX PWM + HBPWM-BOX, here the control output is performed as pulse modulation 0 to 6second duty cycle, where you can control a solinoid expansion valve directly without the need for an external controller. Work with Danfoss AKV/AKVA and Hansen PXV/PXVW pulse modulating liquid refrigerant expansion valves, Coils 24 to 240V AC. Note: HBX-DX/C-R-3-X/PWM, with valve cable for easy electrical connection. HBX-DX-R-3-X/PWM, without valve cable, then the PWM output is connected to PIN3 (blue colour). The HBSSR-BOX is included. Validation of vapor oqality sensor 01 13-04-2018 page
Setting : HBX-DX & HBX-OVC Rod style sensors, operation temp. 10 to 45grd.C Application 3/4 Rod style, DX /OVC sensor 1 Rod style, OVC sensor Zero settings Span settings, DX sensor X range 0.8 to 1.0 Span settings, OVC sensor X range 0.6 to 1.0 Basic settings HBX-DX L160: 42pF +/-1pF L300: XXpF +/-1pF L300: 46pF +/-1pF L160: 15 to 25pF default: 20pF L300 : 25 to 35pF default: 30pF L160: 50 to 400pF default: 300pF L300: 80 to 600pF default: 500pF L300: 50 to 300pF default: 200pF Filter: 5sec., Run-IN: ON Basic settings HBX-OVC Alarm: 0.8, Alarm delay: 10sec Filter: 10sec., Run-IN: OFF Alarm: 0.6, Alarm delay: 60sec. Filter: 10sec., Run-IN: OFF Alarm: 0.6, Alarm delay: 60sec. Note: Data above is for NH3 operation, temperature from 10 to 45grd.C Higher operating pressures require a different adjustment of the zero value (dry vapor/gas) because of a higher relative density, for example will a change in pressure from 0.2bar to 5bar resulting in a changes from 42pF to 44pF (HBX-DX, Rod 160mm) By performing the zero calibration at desired operating temperature / pressure, compensation will be done automatically and ensure highest measuring accuracy. HBX-DX mk2 sensors can be supplied with temperature input for temperature compensation. We recommend compensation especially on CO2 systems where high pressure variations occur during startup. HBOVC 1 HBDX & HBOVC 3/4 HBX (CO2/HFO/HFC type) CAUTION! Factory settings do not guarantee safe operation since the configuration parameters depend on the system design. HB Products A/S Bøgekildevej 21 DK8361 Hasselager support@hbproducts.dk www.hbproducts.dk Validation of vapor oqality sensor 01 13-04-2018 page