Effects of external perturbations on dynamic performance of carbon dioxide transcritical power cycles for truck engine waste heat recovery
19
Citation
25
Reference
10
Related Paper
Citation Trend
Keywords:
Overshoot (microwave communication)
Thermal expansion valve
Transcritical cycle
Settling time
Valve timing
Overshoot (microwave communication)
Thermal expansion valve
Gas engine
Cite
Citations (0)
Overshoot (microwave communication)
Settling time
Servomechanism
Tracking error
Cite
Citations (7)
-High oscillation in industrial processes is something undesired and controller tuning has to solve this problems. PDF and PIDF are controller modes which are expected to overcome this problem. This research work has proven that the PIDF is the genuine solution for the high level process oscillation. A second order process of 85.45 % maximum overshoot and 8 seconds settling time is controlled using a PIDF controller (through simulation). The controller is tuned by minimizing the sum of absolute error of the control system using MATLAB. A functional constrains is imposed on the maximum percentage overshoot. The result was cancelling completely the process oscillation with a zero overshoot and a 0.62 seconds settling time. The performance of the PIDF controller is compared with the classical PID controller with the same process. Keywords—PDF controller, PIDF controller, overshoot, maximum overshoot, gain, and settling time.
Overshoot (microwave communication)
Settling time
Oscillation (cell signaling)
Open-loop controller
Rise time
Cite
Citations (6)
In this paper, a transcritical heat pump using CO2 as the refrigerant was developed, and the heating performance test experiment was carried out in the standard bus air conditioning performance enthalpy difference laboratory to explore the influence of outdoor temperature, compressor speed and electronic expansion valve (EEV) opening on the performance of the heat pump system. Operating at −25 °C/20 °C (outdoor temperature is −25 °C, indoor temperature is 20 °C), the heating capacity (Q) of the CO2 heat pump is 10.5 kW, the coefficient of performance (COP) is 1.24, indicating that the system can also effectively save energy under ultra-low temperature conditions. As the compressor speed rises, the COP of system drops sharply, so the compressor operating frequency should be reduced as much as possible under the premise of satisfying the Q and outlet air temperature (Ta.out). Increasing the opening of the EEV can effectively reduce the compressor exhaust temperature (Tcom.out) and pressure(Pcom.out) to ensure the safe and stable operation of the system.
Coefficient of performance
Thermal expansion valve
Transcritical cycle
Cite
Citations (9)
Today, it is seen that increasing environmental pollution is getting ahead of the increasing energy need. Therefore, more environmentally friendly and more economical refrigerants are needed. In this context, carbon dioxide appears as a natural refrigerant in cooling systems and heat pump (HP) systems, and it has been widely used in recent years. In this study, a single-stage heat pump system with a CO2 refrigerant, with a transcritical cycle, has been experimentally studied. The system is designed as a water-to-water heat pump. The performance of the system has been determined experimentally. In the system, capillary pipes with a diameter of 2.00 mm and two different lengths are used. It is aimed to create different evaporation pressures with two capillary tubes. The first capillary tube is 2.40 m long and the second is 1.20 m long. Gas cooler pressures, gas cooler and evaporator cooling water mass flow rates were kept the same for both cases. A certain gas charge was made and measurements were made for both cases. Thermodynamic analysis and comparison of the system were made. In the short capillary tube system, it was observed that the COPHP value was 7.2% higher, the CO2 mass flow rate increased by 9.1% to achieve the same gas refrigerant pressure value, and the power consumption in the compressor decreased by 1.8%. In addition, the gas cooler outlet temperature, the evaporator outlet temperature and the change in ambient temperatures, as well as the exergetic destruction and exergetic efficiencies in the system and system components are presented in figures with EES.
Transcritical cycle
Thermal expansion valve
Coefficient of performance
Cite
Citations (2)
From the viewpoint of global environmental protection and energy-saving, the research and development on high-efficiency heat pump systems using environment-friendly refrigerants have become one of the most important issues in the air-conditioning and refrigeration sector. Carbon dioxide (R744) is regarded as a candidate for alternative refrigerant, and R744 heat pump water heater has already been commercialized. However, due to its low critical temperature and high operating pressure, there are still many problems that remain to be solved. One of the agenda is the prediction method for cycle performance when R744 is used as the working fluid of air conditioning equipment. In this study, a steady-state model of the R744 transcritical cycle for air conditioning has been developed to estimate the cooling and heating performance. This cycle consists of a rotary compressor, a fin-tube gas cooler, a fin-tube evaporator, an expansion valve and connecting tubes. The cycle performance has been examined by varying the specifications of heat exchangers and the degree of refrigerant superheat.
Transcritical cycle
Thermal expansion valve
Coefficient of performance
Cite
Citations (1)
Abstract In this paper, a simple design method is presented to adjust the parameters of a proportional-integral derivative PID controller to be applied to different systems. In this method, PID controller is designed based on setting the optimal proportional gain according to the desired performance (settling time, overshoot). Determining the other parameters of the PID controller by adjusting the optimum ratio gain (k p ) in a stable loop that minimizes the settling time (t s ) and the error rate of the overshoot (M p ) constitutes the basis of the method. The Routh Rurwitz criterion is used to guarantee stability. The performance of the controller designed with the proposed method has been evaluated on three different transfer functions. With this method, the PID controller works successfully without destroying parameters and without complex mathematical formulation. It has been observed that the proposed method provides better closed loop performance compared to the methods reported recently.
Settling time
Overshoot (microwave communication)
Rise time
Cite
Citations (1)
Abstract This article presents experimental results on the effect of refrigerant distribution in microchannel a parallel flow evaporator that is part of an air conditioner/heat pump system that operates with CO2 in transcritical cycle. The improvements of COP achieved are as high as 20%. Three different refrigerant feeding strategies are discussed.
Microchannel
Transcritical cycle
Thermal expansion valve
Cite
Citations (15)
Due to the environmental concerns regarding traditional refrigerants, carbon dioxide (CO2) is being studied as an alternative refrigerant in HPWHs. In this study, a commercially available, transcritical CO2 HPWH was numerically and experimentally assessed. This included developing a model of the CO2 HPWH and calibrating it with experimental data. The model was theoretically verified and utilized to predict the cycle pressures and compressor isentropic efficiency. While the predicted discharge pressures were within the expected range, the significant biases indicate that further work is required to increase the model accuracy. Additionally, study of the control system indicated that the water outlet temperature controls the water pump, the ambient temperature controls the compressor and evaporator fan, and that the expansion valve controls the high side pressure. Lastly, the performance data shows that the HPWH achieves the best performance at ambient air temperatures above 0°C and at water inlet temperatures below 30°C.
Transcritical cycle
Thermal expansion valve
Discharge pressure
Isentropic process
Cite
Citations (1)
It is widely known that real nonminimum phase zeros lead to step response undershoot, and that the size of the undershoot necessarily tends to infinity as the settling time tends to zero. In this note, we show that the presence of two or more real nonminimum phase zeros can lead to step response overshoot in addition to undershoot. A lower bound on the overshoot is derived, and it is shown that the overshoot, like the undershoot, necessarily tends to infinity as the settling time tends to zero. The results are derived for single-input-single-output linear time-invariant continuous-time systems, and apply to both open-loop control and general two degree-of-freedom closed-loop control
Overshoot (microwave communication)
Settling time
Pole–zero plot
Minimum phase
Infinity
Cite
Citations (48)