Evaporator Fan Research Articles

Experimental investigation and validation on an air-source heat pump frosting state recognition method based on fan current fluctuation signal and machine learning

Thick frost on the evaporators of air-source heat pumps and refrigeration systems can degrade system performance. Defrosting in time based on precise frosting state recognition method is of great importance. Indirect measuring recognition method with low accuracy is widely used in commercial systems, for cheapness and simpleness, needing improvement urgently. While accurate direct measuring methods are usually expensive and complicated. Therefore, a novel frosting state recognition method with high accuracy is proposed, which can be realized with a simple current sensor. The method is based on the micro fluctuation in the evaporator fan current (rather than current amplitude) caused by the perturbed air due to frost. An experimental setup is built to obtain fan current samples. Combining three feature extraction approaches and three classifiers, four frost state recognition methods using fan current fluctuation are merged. They are compared and studied based on the experimental samples. Results show original signal + 1D-CNN method has the best identification performance, reaching 95.74 ± 1.73 % accuracy at −10 °C evaporator air temperature. It reveals 94.53 ± 1.06 % accuracy in a temperature range of −5∼-20 °C, and 94.73 ± 1.00 % accuracy for another fan with the same model. The method has significant improvement in performance and good potential for further study and application.

Operating parameters optimization of a thermosyphon and compressor system used in 5G TBS

The free cooling technology is an effective way to reduce the energy consumption of an increasing number of 5G telecommunication base stations. In this paper, a parallel hybrid cooling system of thermosyphon and vapor compression for free cooling used in 5G telecommunication base stations has been proposed. The energy efficiency ratio (EER) is experimentally investigated in a simulated base station under different working conditions and operating parameters. The results indicate that operating parameters such as setpoints of return air temperature, evaporator and condenser fan speeds can significantly affect the natural cooling source utilization ratio of the hybrid cooling system, thereby affecting the EER of the system. When the outdoor temperature is less than 20 °C, the variation of evaporator fan speed will have a significant impact on the operating mode of the system. An appropriate evaporator fan speed can reduce the proportion of compressor operating time to 0%. At an outdoor temperature of 15 °C, optimizing the evaporator and condenser fans speeds can improve the EER by 60% and 52%, respectively. However, when the outdoor temperature exceeds 25 °C, the system always operates in air-conditioning mode, resulting in the system's EER being minimally affected by the fans speeds. While ensuring the safe operation of communication equipment, optimizing the evaporator fan speed and setpoint temperature simultaneously can increase EER from 3.18 to 17.19.

Refrigeration components sizing tool for design of domestic refrigerators (ReSiCo): Demonstration in full scale

Domestic refrigerators have caused various energy-related issues for years. Replacing old refrigerants, using more flexible components, and reducing power consumption have been the main concerns of manufacturers. It is an improper use of energy and resources to implement each new change in the construction of the refrigeration cycle by trial and error. Therefore, virtual labs can assist designers in investigating potential changes before implementing that in practice. This work describes the procedure by which a flexible software is developed to simulate each component of the refrigeration cycle and predict the desired variables in an efficient time. In this software, the amount of refrigerant charge and the degree of superheat are provided as input variables; geometrical parameters for each component are considered in detail. The tube-by-tube and map-based methods are implemented to model the heat exchangers and compressor, respectively. Heat transfer between the suction line and capillary tube is simulated as well. Eventually, the performance parameters with all thermodynamic properties of the cycle at any arbitrary location can be reported as outputs. The case studies showed that the coefficient of performance will increase from 1.58 to 2.1, and from 2 to 2.2 by tuning the suction-line-heat-exchanger and evaporator fan speed, respectively.

Investigation of the effects of fan control technique on energy consumption in industrial refrigerated display cabinet: An experimental study

With the increase in electricity consumption and price, energy efficiency in industrial refrigeration systems becomes an even more important issue. The performance of the industrial refrigeration system can be reported by creating energy labeling according to the energy efficiency index value. In this study, the industrial refrigeration system was evaluated in terms of energy performance with proposed a fan control technique and performed an environmentally friendly design using propane (R290) refrigerant. In addition, a new control process was developed for the management of evaporator and condenser fans, and the effect of this process on the cooled package temperatures and energy consumption was investigated. With this new technique, a 25.2% improvement was achieved in the total energy consumption of the industrial refrigeration system. It was observed that the cooled package temperatures were between −1 and +5°C throughout the experiment. The EEI value of the industrial refrigeration system has increased from class “E” to class “D” using a new control technique.

Grey-box Fault Models and Applications for Low Carbon Emission CO2 Refrigeration System

CO2 refrigeration systems have attracted more attentions in recent years because of their zero-carbon emission advantages compared with traditional refrigerants. These systems are widely used in certain commercial buildings such as supermarkets. However, very limited energy studies have been done for such refrigeration systems under faults. This study investigated five common faults for supermarket transcritical CO2 refrigeration systems with display cases. The following major tasks were implemented for this study. (1) Five fault models (gray-box format) regarding the power consumption and supply air temperature were proposed for low- and high-temperature display cases, respectively. The models cover: ice accumulation on evaporator coil, evaporator fan partial failure, expansion valve failure, display door open, and condenser blockage. (2) These fault models were calibrated with field tests, and the modeling accuracies were in good agreement with measurement datasets. (3) The proposed fault models demonstrated more than 90% of fault detection for Fault Detection and Diagnostics (FDD) purposes for both field measurement and simulated data.

Experimental Performance Analysis of R1234yf in an Air-Conditioning System as Substitute of R134a

In this work, R1234yf is tested in an air-conditioning system as a proposed alternative to R134a. The system is tested at 30, 35, 40, 45 and 50[Formula: see text]Hz evaporator fan frequency to cool the air entering into the evaporator section at a fixed temperature of 35∘C. The system is charged with 600, 700, 800, 1000 and 1200[Formula: see text]g of each refrigerant. The charge mass of 800 grams gives the best performance for both refrigerants. Also, R1234yf has higher COP, exergetic efficiency, second law efficiency, and lower compressor power consumption. Both refrigerants operate at a moderate range of compressor discharge temperature of 85∘C.

Case study: Experimental characterization of noise and vibration sources in a refrigerator

The sources of noise and vibration of a refrigerator are characterized by means of laboratory measurements. Three different elements are considered: compressor, evaporator fan, and condenser fan. Both the radiated acoustic energy and the mechanical power injected to the refrigerator structure are measured. Acoustic intensity maps on the refrigerator faces at different frequencies are also provided They are helpful in visualizing the more problematic zones in terms of noise emis- sion. The devices are tested in vacuo or working inside the refrigerator. The provided information can be used as input data for vibroacoustic simulation models such as statistical energy analysis. It is also of interest in order to improve the refrigerator acoustic design.

Enhanced heat transfer in a refrigerated container using an airflow optimized refrigeration unit

The present study numerically investigates the airflow and heat transfer characteristics in a conventional refrigerated container (CRC), and an improved refrigerated container (IRC) loaded with cargoes by modeling the refrigeration unit and the cargoes in the container as porous media. The IRC design is based on a previous study by the current authors, where the airflow in the refrigerated container was enhanced by improving the refrigeration unit design. The airflow inside the refrigerated container is simulated by using the fan pressure jump boundary conditions at the location of the evaporator fans in the refrigeration unit. The CRC and IRC are simulated for three fan pressure jump conditions of 50, 100, and 150 Pa. Initially, the airflow and heat transfer results under 50 Pa fan pressure jump condition are compared for CRC and IRC to estimate the enhanced heat transfer in IRC. Then, the behavior of the heat transfer characteristics in CRC and IRC under increasing fan pressure jump conditions is studied by comparing the results of CRC and IRC under the three fan pressure jump conditions. Results show that the heat transfer and the temperature homogeneity of the cargoes in IRC are significantly improved due to the enhanced airflow by the improved design of the refrigeration unit in IRC.

Assessing the performance limits of a variable-speed residential heat pump system

Most of the ducted split-type heat pump systems in the world feature fixed-speed compressors and fans. To meet forthcoming minimum energy rating requirements, reduce operational costs of the heat pump, and increase environmental sustainability, the efficiency of heat pump systems must be improved. Variable-speed equipment offers significant advantages for load modulation and has the ability to increase the seasonal performance significantly. Additionally, novel electrical motor technologies, such as permanent magnet (PM) motors can reduce the power consumption of the drives by up to 25-55% compared to the widely used permanent split capacitor (PSC) motor.In this study, a ducted fixed-speed heat pump system with a cooling capacity of 17.6 kW and a seasonal coefficient of performance (SCOP) rating of 4.11 is analyzed to quantify the theoretical performance limits that could be obtained by increasing the motor efficiency of the condenser fan, the evaporator fan and the compressor. Furthermore, the performance increase by replacing the fixed-speed components with variable-speed equipment is evaluated. A detailed charge-sensitive system simulation model that was previously developed by the authors and validated using experimental data obtained with the same unit was employed to carry out parametric studies to evaluate the impact of variable-speed compressor and indoor/outdoor fans on the SCOP rating.The study showed a 0.9% improvement of SCOP with every percentage increase of compressor motor efficiency. The dependence of the evaporator fan and condenser fan motor efficiency on SCOP was lower, but considering the generally low motor efficiencies of these components, a noticeable efficiency gain can be achieved. In variable-speed equipment, the motor efficiency of the component at minimum operational point was the significant factor on SCOP. The motor efficiency at intermediate and maximum speed had only marginal effects on the SCOP. This showed the importance of equipment with high motor efficiencies at low speeds for ducted split-system heat pumps. The change of the fixed-speed system to a fully variable-speed heat pump resulted in a high gain of SCOP, proving the superiority of a variable-speed system. Overall, the model predicted an SCOP gain of 35% when changing the system to a fully variable system with state-of-the-art high efficient motors.

Performance characteristics of a heat pump using renewable transcritical CO2 refrigerant for heating water

ABSTRACT Among non-toxic and inflammable working fluids, carbon dioxide (CO2) proving a possible choice of refrigerant is gaining full status because of its reducing capacity of global warming and ozone depletion. Heat pump (HP) equipment uses energy more rationally to heat water by reducing emissions and global warming caused by conventional refrigerants. HP capability demands an environmentally friendly refrigerant for their full utilization and high energy saving as well to attaining higher coefficient of performance (COP) without much design corrections. CO2 is checked for sustainability to eliminate the standardized refrigerants such as chlorofluorocarbons (CFC) and hydro-CFC. In this work, the performance of CO2 as an alternate refrigerant in HP for heating water at different pressure, flow rates, evaporator fan speed and preheating have been investigated. HP is accommodated with two condensers. The results showed that the increased mass flow rate had increased COP, overall heat transfer (HT) coefficient (U) and HT. However, logarithmic mean temperature difference was decreased for increasing evaporator’s fan speed and pressure. The outlet water temperature (TWO) of second condenser increased with decreasing water flow rate. Improved COP, HT and TWO of HP are observed from the experimental evaluation in case of preheating of water.

Dynamic performance analysis of inverter-driven split air conditioner

Abstract Variable speed technology has a great potential for improving energy efficiency and performance of vapor compression refrigeration cycle. Therefore, the study of dynamic characteristics of the refrigeration cycle using this new technology becomes essential. This study experimentally investigates the dynamic behavior of a split R-410A air conditioner comprising variable speed compressor, variable speed condenser fan, three speed evaporator fan and electronic expansion valve. The characteristics of the conditioner have been presented during the startup and shutdown periods. Furthermore, the effect of changing evaporator fan speed during the running of the conditioner has been illustrated and discussed. The influence of evaporator and condenser inlet air temperatures on the power consumption and coefficient of performance of the conditioner has also been investigated. The experimental results show that increasing the condenser entering air temperature by 7 °C, the power consumption has been increased by 18% and the coefficient of performance decreased by 15%.

Real-time efficiency optimization of a cascade heat pump system via multivariable extremum seeking

In this paper, the Extremum Seeking Control (ESC) is proposed as a model-free real-time optimizing control strategy for efficient operation of a cascade air source heat pump (CASHP). ESC is a model-free real-time optimization framework, which can search for the unknown and slowly varying input setpoint for optimizing specific performance index. The ESC strategy is realized for the scenarios of power minimization and COP maximization, respectively. For the power minimization, the ESC optimizes the setpoints of intermediate temperature and the superheat setpoints for the high-temperature and low temperature cycles; while for the COP maximization, the manipulated inputs are the compressor speeds of the high-temperature and low-temperature cycles and the evaporator fan speed. To validate the effectiveness of the proposed ESC strategy, a Modelica based dynamic simulation model of a CASHP water heater is built with Dymola and TIL Library. The CASHP is designed to provide the discharge water temperature of 85 °C, with R404A and R245fa as the refrigerants for the low temperature cycle and high temperature cycle, respectively. Under both fixed and realistic ambient temperature profiles, the simulation results show satisfactory convergence performance for both steady-state and transient characteristics. Thus, the feasibility of the proposed CASHP control strategy is validated.

A sequential approach for achieving separate sensible and latent cooling

Abstract Separate sensible and latent cooling (SSLC) is a potentially beneficial approach to improve the efficiency of air conditioning systems; however, the complex configuration of existing and proposed SSLC systems increases installation and maintenance costs, limiting their widespread use in new construction and building retrofit opportunities. In this paper, a sequential SSLC system is proposed to realize the separation of sensible and latent loads by switching a single vapor compressor cycle between two modes (low-SHR and sensible only). This effect is achieved by applying readily available variable-speed equipment at a high compressor speed and a low fan speed to achieve the low-SHR mode operating for dehumidification. This is followed by a sensible only mode to cool the air, which is achieved through a low compressor speed and a high evaporator fan speed. To predict the performance of a sequential SSLC system, a numerical model has been developed and validated. Using this numerical model for energy consumption and optimization studies, it is found that the sequential SSLC system has the potential to save 6.9% to 11.5% energy compared to a traditional cooling system.

Experimental characterization of demand response in a refrigerated cold room

Abstract Demand response (DR) is one of the energy management strategies that can relieve the strain on power grid by balancing the energy consumption and production. Cold storage in warehouses and cold rooms, due to the high thermal inertia contained in the stored products, is a promising solution for applying DR. For cooling applications, different DR strategies can be considered: stopping evaporator fans or stopping the refrigeration machine, producing more cooling power during off peak hours and reducing the cooling operation during on peak hours, etc. However, these scenarios need to be carefully applied to respect the temperature regulation in order to maintain food quality and security. Moreover, DR application might lead to an increase of power demand when restarting the cold machine – the postponing power effect or an over-consumption of energy for the recovery of the temperature level before DR – the postponing consumption effect. This paper presents an experimental investigation of DR application in a loaded cold room; the impact of several DR parameters: product load, outside temperature, set point temperature and DR duration were assessed. The results showed that DR has limited impact on the stored product: a maximum increase of 1.1 °C at the product core after 3 days of DR application, one DR per day. However, a cumulative effect of DR applications on product temperature was observed. The indicators of the postponing power effect and consumption variation showed important impacts of studied parameters on the system behaviour during DR application.

PERBANDINGAN COP AC SPLIT KAPASITAS 1 PK MENGGUNAKAN REFRIGERANT R410a DAN R32 DENGAN VARIASI KECEPATAN FAN EVAPORATOR

Air Conditioning Split or AC Split is one of the air conditioning system that works by using a vapor compression system. The vapor compression system is one of the most cycles used for mechanical refrigeration systems, while the vapor refrigerant will be compressed by the compressor as the main component in addition to other components such as condensers, expansion valves and evaporators. This research focuses on AC Split Coefficient of Performance (COP) with Comparison of Refrigerants R410a and R32 with variations speed based on the Evaporator Fan speed. This analysis method uses two AC Split each capacity is 1PK with two different of refrigerants R32 and R410a, as well as varying in Low, Medium and High-level speed with air flow velocity in each mode respectively 1.2 m/s, 1.5 m/s and 1.9 m/s. From the result that COP on R410a refrigerant is 8.13 and COP on R32 refrigerant is 5.3. And also, the efficiency of R410a is 72.8% and R32 is 70.67%. So, AC Split with refrigerant R410a has better COP compared with AC Split with refrigerant R32. Keywords: COP, AC Split, Refrigerants, R410a, R32, Efficiency

Design, worst case study, and sensitivity analysis of a net-zero energy building for sustainable urban development

This paper presents a trigeneration facility based on a biogas driven gas turbine cycle for electricity production and an air to water heat pump for simultaneous extraction of cooling and potable water, and evaluates its robustness and effectiveness under different climatic conditions and variable demands. The air to water heat pump, which consists of an inside evaporator fan, expansion device, condenser, evaporator, and a compressor, is installed for supplying the cooling load of a hospital building in summer. In the refrigeration cycle, R134a absorbs heat from the inside warm air for space cooling and releases it to the saline water for driving a desalination process. Maximum values of cooling and electrical demands of a standard hospital building, where is located in south of Iran, over the hottest day of 2018 are considered for the worst case implementation. Engineering equation solver and general algebraic mathematical modeling system are employed to develop the non-linear optimization strategy, find the best operating point of the air to water heat pump based trigeneration plant, and minimize its energy cost under the greatest load level. Moreover, the sensitivity of the gained output ratio of desalination cycle to the relative humidity of the air entering and leaving the humidifier, the dehumidifier and humidifier effectiveness, and the top and bottom temperatures are comprehensively analyzed. The relative humidity of air entering the humidifier and the larger dehumidifier effectiveness have the significant effects on increasing the gained output ratio of the desalination cycle. Due to intense solar irradiation in summer, the seawater temperature naturally increases, which results in larger gained output ratio and higher mass flow rate of pure water.

A potential approach for reducing the R290 charge in air conditioners and heat pumps

This study presents a potential approach for reducing the propane (R290) charge required in air conditioners (ACs) by introducing micro bare-tube heat exchangers as the condenser and evaporator. A theoretical model is developed to predict the performance of a split AC unit, and the unit is tested in an experiment. The split AC unit is tested under the ISO 5151:2017 standard capacity rating test condition in a psychrometric room (outdoor conditions: 35 °C dry bulb/24 °C wet bulb; indoor conditions: 27 °C dry bulb/19 °C wet bulb). The compressor input electricity power is 928 W with 62-W condenser fan power and 82-W evaporator fan power. The test cooling capacity is 3645 W with a system coefficient of performance of 3.40. The stainless steel micro-tube heat exchanger has a 0.58-mm outer diameter and 0.38-mm inner diameter. Owing to the use of micro bare tubes, the optimal propane charge is 248±5 g, which follows the EN378-1:2016 regulation. The use of micro bare-tube heat exchangers in a split AC unit could be a potential approach to reducing the R290 charge required in ACs and heat pumps.

Experimental Investigation of a Walk-in Refrigerator Performance using R290 as a Retrofit for R22

An experimental performance study is performed on a refrigeration system equipped with a scroll compressor and tested with R22 using an electronic expansion valve (EEV) as an expansion device and controlled by proportional-integral-derivative (PID) control method. The system is tested at [Formula: see text]C, [Formula: see text]C, [Formula: see text]C, 0[Formula: see text]C and 4[Formula: see text]C evaporator air temperature and 20[Formula: see text]C, 25[Formula: see text]C and 30[Formula: see text]C condenser inlet water temperature at 50[Formula: see text]Hz compressor driving frequency and 50[Formula: see text]Hz evaporator fans driving frequency. R22 reached the set point at all temperatures except [Formula: see text]C evaporator temperature with 30[Formula: see text]C condenser temperature due to the severe increase in the compressor discharge temperature that could result in the lubricating oil burnout. Then, the system is retrofitted with a reciprocating compressor especially designed to be used with R290 and tested with R290 at the same evaporator and condenser temperatures using EEV as an expansion device. R290 reached all set points at all evaporator and condenser temperatures. Also, R290 was able to reach all evaporator temperatures at higher condenser temperatures, 35[Formula: see text]C and 40[Formula: see text]C, and this will be discussed in future work. The results show that using R290, the pulldown time decreases by 30.3–71.4%, the ON time ratio decreases by 1–23.6%, the compressor discharge temperature decreases by 46.6–81[Formula: see text]C, the refrigerant mass flow rate decreases by 28.8–50.4%, VRC decreases by 15.2–32.5%, the compressor power consumption decreases by 34.4–44.3% and coefficient of performance (COP) increases by 35–115.5%.

Supermarket system characteristics and operating faults (RP-1615)

Supermarkets undergo various types of operating faults that can require costly preventive maintenance, service, and repairs. Because supermarkets are growing in number and in the variety of system types and characteristics, information about common faults and equipment is essential prior to investing effort on the development of new fault detection and diagnostics (FDD) methods or other improvements to system design and operation. A study was conducted to investigate supermarket equipment characteristics, such as the prevalence of central vs. distributed systems, condenser types, control strategies, and common operating faults such as refrigerant leakage, failed evaporator or condenser fans, failed compressors, etc. The data come from four sources: expert surveys, facility management system messages, service calls, and service records. Some of the results of the study are that centralized direct expansion systems with on/off compressor capacity control strategy and air-cooled condensers are the most common system types and refrigerant charge problems are the most common source of equipment failure. Case-related problems, in aggregate, are the most frequently occurring faults in supermarkets.

Model design of condenser for solar assisted geothermal cooling system using software simulation

Condensers are extensively used in refrigeration, air-conditioning and power generation systems. Condenser for the solar assisted geothermal cooling system is designed by using software simulation of condenser’s geometrical and flow parameters. The geothermal cooling system is designed to reduce electricity consumption of compressor during peak hours during the summer period in hot weather condition. The subsurface temperature of the earth around 5–6-m depth is fairly constant throughout the year which fulfills the requirement of cooling inside the building or residence by using water as a heat exchanging medium. Water is circulated in closed loop system buried into subsurface which sinks the heat of refrigerant from condenser inside the subsurface soil. The condenser is designed by comparing results obtained from (1) manual calculation (2) simulation by CHEMCAD software. In order to have a good and optimized design, manual and software-based calculations should be carried out simultaneously and verified with each other. It is found that results obtained from both calculations are approximately same with a minor difference. The geometry and flow parameter of the condenser is determined on the basis of surrounding temperature. The solar panel is used for power generation to reduce electricity consumption by the compressor, pump, and evaporator fan coil. This provides the hybrid solar assisted geothermal cooling system.