Condenser Fan Speed Research Articles

Controller Design for Air Conditioner of a Vehicle with Three Control Inputs Using Model Predictive Control

Fuel consumption optimization is a critical field of research within the automotive industry to meet consumer expectations and regulatory requirements. A reduction in fuel consumption can be achieved by reducing the energy consumed by the vehicle. Several subsystems contribute to the overall energy consumption of the vehicle, including the air conditioning (A/C) system. The loads within the A/C system are mainly contributed by the compressor, condenser fan, and underhood aerodynamic drag, which are the components targeted for overall vehicle energy use reduction in this paper. This paper explores a new avenue for A/C system control by considering the power consumption due to vehicle drag (regulated by the condenser fan and active grille shutters (AGS)) to reduce the energy consumption of the A/C system and improve the overall vehicle fuel economy. The control approach used in this paper is model predictive control (MPC). The controller is designed in Simulink, where the compressor clutch signal, condenser fan speed, and AGS open-fraction are inputs. The controller is connected to a high-fidelity vehicle model in Gamma Technologies (GT)-Suite (which is treated as the real physical vehicle) to form a software-in-the-loop simulation environment, where the controller sends actuator inputs to GT-Suite and the vehicle response is sent back to the controller in Simulink. Quadratic programming is used to solve the MPC optimization problem and determine the optimal input trajectory at each time step. The results indicate that using MPC to control the compressor clutch, condenser fan, and AGS can provide a 37.6% reduction in the overall A/C system energy consumption and a 32.7% reduction in the error for the air temperature reference tracking compared to the conventional baseline proportional integral derivative control present in the GT-Suite model.

THE EFFECT OF VARIATIONS SPEED OF THE CONDENSER FAN WITH CONTROL FREQUENCY INVERTER ON THE ICE SLUSH MACHINE APPLICATION

The condenser is one of the main components in the ice slush machine system that functions to removed heat from the system to the environment. In this system, the condenser is equipped with a fan whose rotation speed is modified using an inverter that aims to determine the system performance and condenser capacity at each fan rotation variation of the ice slush machine. There are 3 variations of frequency settings in this system 50 Hz, 40 Hz, and 30 Hz, with equivalent velocity air 3.6, 2.9, and 1.9 m/s respectively. In this study, the performance of the ice slush machine with various condenser fan speed settings was studied including, how long the product temperature is reached, condenser capacity, actual COP, efficiency, and electrical power. The test results show that the fastest product temperature is reached when using a fan speed setting of 1397 rpm, which is 145 minutes with a condenser capacity of 42.36 kW. The highest actual COP is obtained from the fan speed set at 1397 rpm of 2.58 with an efficiency of 57.5% and electrical power consumption of 269.64 W. The fan speed setting at 1090 rpm has a condenser capacity of 33.78 kW, COPactual of 2.46 with an efficiency of 56.2%, and electric power consumption of 272.09 W. The fan speed setting at 711 rpm has a condenser capacity of 21.73 kW, an actual CO of 2.15 with an efficiency of 49.2%, and electric power consumption of 312.71 W.

Model-Based Condenser Fan Speed Optimization of Vapor Compression Systems

Vapor compression systems (VCS) cover a wide range of applications and consume large amounts of energy. In this context, previous research identified the optimization of the condenser fans speed as a promising measure to improve the energy efficiency of VCS. The present paper introduces a steady-state modeling approach of an air-cooled VCS to predict the ideal condenser fan speed. The model consists of a hybrid characterization of the main components of a VCS and the optimization problem is formulated as minimizing the total energy consumption by respectively adjusting the condenser fan and compressor speed. In contrast to optimization strategies found in the literature, the proposed model does not relay on algorithms, but provides a single optimization term to predict the ideal fan speed. A detailed experimental validation demonstrates the feasibility of the model approach and further suggests that the ideal condenser fan speed can be calculated with sufficient precision, assuming constant evaporating pressure, compressor efficiency, subcooling, and superheating, respectively. In addition, a control strategy based on the developed model is presented, which is able to drive the VCS to its optimal operation. Therefore, the study provides a crucial input for set-point optimization and steady-state modeling of air-cooled vapor compression systems.

Management of Condenser Fan Speed and its Influence on the Split Air Conditioner Performance

Energy saving is the challenge of decreasing the quantity of energy consumption needed. This can be done by employing reliable and smart control system. In this article, an experimental study has been carried out to investigate the performance of a split air conditioning unit having a variable speed condenser fan. The rate of heat rejection airflow has been controlled according to the outdoor air temperature via a Proportional Integral Differential (PID) controller. The control algorithm allows increasing the condenser fan speed with the increase of outdoor air temperature and vice verse. The maximum rate of air flow of the fan is 0.43 m3/s at 42ºC outdoor air temperature and the minimum flow is 0.28m3/s. To facilitate variation of refrigerant flow rate according to the evaporator load, the traditional capillary tube was replaced with a suitable thermostatic expansion valve and liquid refrigerant reserve. The influence of condenser airflow modulation and its temperature on the air conditioner performance and also on the compressor power consumption has been investigated and presented at different evaporator loads. It has been found that a 10 % reduction in compressor power is achieved by increasing the condenser air flow by about 50%.

The Thermal Analysis of a Semi-Open Heat Pump Drying System: An Experimental Investigation

One of the key advantages of heat pump (HP) systems is their ability to recover waste heat energy for useful input. In this study, the thermal performance of a heat pump drying system that recovers heat energy from the hot and moist exhaust air from the dryer was designed, constructed, and examined. The performance of this semiopen air source heat pump system was investigated and analysed by varying the refrigerant charge, the condenser fan speed, and the thermal expansion valve orifice size at ambient temperatures ranging from 23 – 26 C. The results indicated that by increasing the charge in the system, the refrigerant mass flow rate, heating capacity and coefficient of performance (COP) of the system increased to a certain maximum point before maximum charging. By increasing the refrigerant charge, both evaporation and condensation pressures of the system increased with condensation pressure indicating more sensitivity on the charge amount before optimum charging than evaporating pressure. The increase in refrigerant charge was observed to decrease the degree of superheat but increase the sub-cooling degree. At an optimum charge, the heating capacity for thermal expansion valve (TEV) of 0.3 mm diameter orifice is 15% greater than that of 0.2 mm diameter orifice. A system power consumption for O0.3 mm orifice was 3% greater than that of O0.2 mm orifice at the optimum charge amount. However, the COP of O0.3 mm orifice was 18% greater than that of O0.2 mm orifice.

Critique of operating variables importance on chiller energy performance using random forest

Chiller systems take up the major proportion of electricity used in commercial buildings. Their energy performance in terms of coefficient of performance (COP) depends on how the controllable and uncontrollable variables change. The aim of this study is to use the random forest (RF) method to measure variables importance and predict the COP. A sophisticated data trend log was carried out on an air-cooled chiller with advanced heat rejection features. The variables measured are: the flow rate of chilled water; the supply and return temperatures of chilled water; the temperature and relative humidity of outdoor air; the compressor power; the evaporating temperature; the condensing temperature; the number and speed of condenser fans staged; the temperatures of air entering and leaving the condenser. The data were logged at 5-min intervals in Aug 2015–Mar 2016. The RF models for different operating modes were validated, with a robust coefficient of determination of 80.52–96.53% for the testing data set. The chiller part load ratio, the condensing temperature, the chilled water flow rate, the heat rejection airflow rate and the wet-bulb temperature are the top five important variables in the prediction of COP. Yet they are not fully considered in typical regression models. Results of this study provide an insight into which variables are important to predict accurately the COP under different energy efficient features. The need of identifying the changing pattern of important variables is ascertained.

Investigation of Optimum Refrigerant Charge and Fans' Speed for a Vehicle Air Conditioning System

In this study, the performance evaluation and optimization of a recently developed battery-powered vehicle air conditioning (BPVAC) system is investigated. A mathematical model is developed to simulate the thermodynamic and heat transfer characteristics of the BPVAC system and calculate the coefficient of performance (COP). Utilizing environmental chambers and a number of measuring equipment, an experimental setup is built to validate the model accuracy and to conduct performance optimization by changing the charge of refrigerant in the system. The model is validated and employed for performance simulation and optimization in a wide range of speed for the evaporator and condenser fans. The modeling results verify that for any operating condition an optimum performance can be achieved by adjusting the speed of condenser and evaporator fans. The optimum refrigerant charge is obtained, and a potential improvement of 10.5% is calculated for the performance of system under ANSI/AHRI 210/240-2008 specifications.

Reciprocating and Screw Compressor semi-empirical models for establishing minimum energy performance standards

The efficiency bar for a Minimum Equipment Performance Standard (MEPS) generally aims to minimize energy consumption and life cycle cost of a given chiller type and size category serving a typical load profile. Compressor type has a significant chiller performance impact. Performance of screw and reciprocating compressors is expressed in terms of pressure ratio and speed for a given refrigerant and suction density. Isentropic efficiency for a screw compressor is strongly affected by under- and over-compression (UOC) processes. The theoretical simple physical UOC model involves a compressor-specific (but sometimes unknown) volume index parameter and the real gas properties of the refrigerant used. Isentropic efficiency is estimated by the UOC model and a bi-cubic, used to account for flow, friction and electrical losses. The unknown volume index, a smoothing parameter (to flatten the UOC model peak) and bi-cubic coefficients are identified by curve fitting to minimize an appropriate residual norm. Chiller performance maps are produced for each compressor type by selecting optimized sub-cooling and condenser fan speed options in a generic component-based chiller model. SEER is the sum of hourly load (from a typical building in the climate of interest) and specific power for the same hourly conditions. An empirical UAE cooling load model, scalable to any equipment capacity, is used to establish proposed UAE MEPS. Annual electricity use and cost, determined from SEER and annual cooling load, and chiller component cost data are used to find optimal chiller designs and perform life-cycle cost comparison between screw and reciprocating compressor-based chillers. This process may be applied to any climate/load model in order to establish optimized MEPS for any country and/or region.

Self-optimizing control of air-source heat pump with multivariable extremum seeking

The air-source heat pump (ASHP) is widely adopted for cooling and heating of residential and commercial buildings. The performance of ASHP can be controlled by several operating variables, such as compressor capacity, condenser fan speed, evaporator fan speed and suction superheat. In practice, the system characteristics can be varied significantly by the variations in ambient condition, operation setpoint, internal thermal load and equipment degradation, which makes it difficult to obtain accurate plant models. As consequence, the model based control strategies for ASHP could limit the achievable energy efficiency. Model-free self-optimizing control strategies are thus more preferable. In this study, a multi-input extremum seeking control (ESC) scheme is proposed for both heating and cooling operation of ASHP. The zone temperature is assumed to be regulated by the compressor capacity, while the expansion valve opening is used to regulate the suction superheat at the given setpoint. The total power consumption of the compressor, the condenser fan and the evaporator fan is measured as input to the ESC, while the ESC controls the evaporator fan speed, the condenser fan speed and the suction superheat setpoint. The proposed scheme is evaluated with a Modelica based dynamic simulation model of ASHP under both cooling and heating modes of operation. Simulation results show the effectiveness of the proposed scheme to achieve the maximum achievable efficiency in a nearly model-free manner.

Design and Testing of a Novel Air-cooled Condenser for Concentrated Solar Power Plants

This paper aims at developing a novel air-cooled condenser for concentrated solar power plants. The condenser offers two significant advantages over the existing state of the art. Firstly, it can be installed in a modular format where pre-assembled condenser modules reduce installation costs. Secondly, instead of using large, fixed speed fans, smaller speed controlled fans are incorporated into the individual modules. This facility allows the operating point of the condenser to change in order to maximise plant efficiency at all times. Two condenser designs were proposed and full-scale prototype modules were manufactured for experimental testing. Both designs comprise a bank of circular finned tubes, coupled to an array of axial fans. The air-side thermal and aerodynamic characteristics were measured using a purpose built steady-state test facility. The measurements were correlated and compared well with existing correlations in the relevant literature, thus validating their use in thermodynamic models to predict power plant performance. A plant performance analysis was conducted combing the experimental measurements with output data from a 50MW concentrated solar power plant. This analysis firstly verified that the plant efficiency can be continually maximised by altering the condenser fan speed. Furthermore, under certain conditions plant output can be increased by over 10% by varying fan speed by 10% of the full speed. The study also provides a comparison of the two designs in terms of their effect on the plant output power. With respect to the thermodynamic efficiency and cost-efficiency, the four row condenser substantially outperforms the initial six row design.

Energy simulation of sustainable air-cooled chiller system for commercial buildings under climate change

Air-cooled chiller systems are commonly used to provide cooling energy in commercial buildings but with considerable electricity consumption. This study demonstrates how to operate the systems with sustainable performance under climate change by applying optimal condenser fan speed control coupled with mist pre-cooling of air entering the condensers. The simulation of system performance was carried out by using EnergyPlus together with an experimentally verified chiller model capable of analyzing advanced control strategies. Weather data under three climate change scenarios in 2020, 2050 and 2080 were considered in evaluating the cooling demand and hourly electricity consumption of an air-cooled chiller system serving an office building. It is found that optimal condenser fan speed control coupled with mist pre-cooling of air-cooled condensers can help maintain a higher coefficient of performance under the warmer future climate, reducing the annual electricity consumption by 16.96–18.58% in the reference weather year and 2080. The ways to implement the sustainable control have been discussed.

Improved energy performance of air cooled centrifugal chillers with variable chilled water flow

This paper considers how to apply optimum condensing temperature control and variable chilled water flow to increase the coefficient of performance (COP) of air cooled centrifugal chillers. A thermodynamic model for the chillers was developed and validated using a wide range of operating data and specifications. The model considers real process phenomena, including capacity control by the inlet guide vanes of the compressor and an algorithm to determine the number and speed of condenser fans staged based on a set point of condensing temperature. Based on the validated model, it was found that optimizing the control of condensing temperature and varying the evaporator’s chilled water flow rate enable the COP to increase by 0.8–191.7%, depending on the load and ambient conditions. A cooling load profile of an office building in a subtropical climate was considered to assess the potential electricity savings resulting from the increased chiller COP and optimum staging of chillers and pumps. There is 16.3–21.0% reduction in the annual electricity consumption of the building’s chiller plant. The results of this paper provide useful information on how to implement a low energy chiller plant.

Tune up of the set point of condensing temperature for more energy efficient air cooled chillers

Abstract This paper presents how to tune up the set point of the condensing temperature for improving the coefficient of performance (COP) of air cooled chillers under various operating conditions. The thermodynamic model of an air cooled screw chiller was developed using the simulation program TRNSYS and validated using the operating data and specifications of the chiller. A new configuration of variable speed condenser fans was proposed for the chiller. An algorithm was introduced to make use of a set point of condensing temperature to determine the number and speed of condenser fans staged at any given cooling capacity. A model was used to investigate how the COP changes with various set points of condensing temperature. It was found that the optimum set point for maximum COP is a function of outdoor temperature and chiller load. Depending on the operating conditions, the COP could increase by 12.1–110.4% when the variable speed condenser fans and the optimum set point of condensing temperature were applied to the existing air cooled screw chillers. This provides important insights into the development of more energy efficient air cooled chillers.

Advanced control of heat rejection airflow for improving the coefficient of performance of air-cooled chillers

Air-cooled chillers are generally the major electricity consumers in air-conditioned buildings in the subtropical climate. This paper presents how the coefficient of performance (COP) of these chillers can be improved by modulating heat rejection airflow via variable speed condenser fans. The thermodynamic model of an air-cooled screw chiller was developed using the simulation program TRNSYS and validated using the operating data and specifications of the chiller. The set point of condensing temperature was used to determine the number and speed of condenser fans staged in various operating conditions. It is found that adjusting the set point in response to the outdoor temperature alone cannot achieve maximum COP when using variable speed condenser fans. Advanced control is proposed for these fans to minimize the chiller electric demand. Compared to the traditional head pressure control with constant speed condenser fans, the use of variable speed condenser fans with the advanced control enables the chiller COP to increase by 4.0–127.5%, which corresponds to a decrease of 1.8–154.6 kW in the chiller electric demand. This provides important insights into how air-cooled chillers can operate more efficiently.