Virtual sensor of insufficient lubrication in variable speed compressors

The ability to modulate the compressor’s speed and adapt the capacity to the load has permitted to decrease the annual energy consumption in many applications. However, in the compressor, having the correct lubrication at high speeds usually imply having insufficient lubrication at low speeds. This fact has to be considered by manufacturers as it limits the speed range of the compressor. In this study, a methodology to establish the working limit of a compressor is proposed. It is based on the specific consumption surface of the compressor and no oil circulation measurements are required. A compressor working between 6600 and 900rpm with propane and POE oil has been used to test the proposed methodology. The results show that lubricating issues in this compressor start at 1800rpm and rise as speed decreases.The authors would like to acknowledge the Spanish “MINISTERIO DE ECONOMIA Y COMPETITIVIDAD”, through the project ref- ENE2017-83665-C2-1-P “Maximización de la eficiencia y minimización del impacto ambiental de bombas de calor para la descarbonización de la calefacción/ acs en los edificios de consumo casi nulo” for the given support. In addition, Ruben Ossorio would like to thank the Spanish government for his PhD scholarship with reference PRE2018-083535

Evaluación exergética de un ciclo de autocascada con eyector para aplicaciones de ultrabaja temperatura

El uso de ciclos eyectores en sistemas con R744 ha sido estudiado en los últimos años mostrando su potencial de mejora, siendo una tecnología implementada a nivel comercial. Existen otras aplicaciones como los frigoríficos de ultra baja temperatura (ULTR) en los que, como consecuencia de trabajar a relaciones de presión muy altas, el uso del eyector podría representar también un potencial de mejora. Hoy en día, con el fin de superar la alta diferencia de temperatura con costos razonables, se implementan configuraciones conocidas como sistema de refrigeración en auto cascada. En este estudio se considera el potencial de mejora del uso de un eyector en el ciclo de autocascada ULTR. El potencial de mejora se ha analizado mediante el estudio de las irreversibilidades que se producen en los diferentes elementos del ciclo mediante un enfoque exergético. Además, se discute el efecto de la temperatura de evaporación sobre el potencial de mejora

Evaluación exergética de un ciclo de autocascada con eyector para aplicaciones de ultrabaja temperatura

El uso de ciclos eyectores en sistemas con R744 ha sido estudiado en los últimos años mostrando su potencial de mejora, siendo una tecnología implementada a nivel comercial. Existen otras aplicaciones como los frigoríficos de ultra baja temperatura (ULTR) en los que, como consecuencia de trabajar a relaciones de presión muy altas, el uso del eyector podría representar también un potencial de mejora. Hoy en día, con el fin de superar la alta diferencia de temperatura con costos razonables, se implementan configuraciones conocidas como sistema de refrigeración en auto cascada. En este estudio se considera el potencial de mejora del uso de un eyector en el ciclo de autocascada ULTR. El potencial de mejora se ha analizado mediante el estudio de las irreversibilidades que se producen en los diferentes elementos del ciclo mediante un enfoque exergético. Además, se discute el efecto de la temperatura de evaporación sobre el potencial de mejora

Efficiency characterization of a variable speed compressor

[EN] Heat pump systems have been spreading into the heating and air conditioning industry as they offer an affordable, efficient and reliable solution. They are considered by the EU as the solution to follow in heating and cooling in order to reach the objectives in reduction of CO2 emissions. As a consequence of that, there is a growing interest in the development of more efficient heat pump systems which has motivated the introduction of many technical innovations in the last 10 years. Among these innovations, the introduction of inverter system has been quite popular. This technology could imply a significant improvement when the system has to work at non-design conditions. However, in the standards there is limited information about the characterization procedure of these systems (i.e. EN 13771-1 only refers to fixed speed or vapour injection compressors) and compressor-inverter system are characterized as a single unit. In that context, it is typical to assume a fixed power loss factor of 3-5% in the inverter. That power loss factor is considered when designing a new system but could differ in the final appliance, especially when the system runs at low speed. In conclusion, the knowledge around variable speed compressors is limited and the system is usually studied as a black box. In this study, the power of a variable speed compressor and its corresponding inverter have been measured separately in a calorimeter test bench according the specifications of the norm EN 13771-1. From these measurements, it has been possible to determine the efficiency of the compressor and the inverter independently. From these results, the aim of the study is to provide a complete analysis of the performance of a variable speed compressor system. The experimental analysis was carried out using the same compressor with two different models of inverter with the same commutation technology. The study consisted in a battery of tests in which the same compression conditions were maintained while the rotation speed of the compressor were modified from 30rps to 120rps. The results of the paper show that the speed of the compressor and the chosen inverter brand has a high effect on the efficiency. Moreover, these results can be applied to get the efficiency curve of an inverter and point out the error that can be made by designers when considering a fixed 3-5% power loss. And last but not least, the study can also set the bases for other investigations involving the reductionOssorio-Santiago, RJ.; Navarro-Peris, E.; Gonzálvez-Maciá, J.; Albaladejo, P.; López-Navarro, A. (2019). Efficiency characterization of a variable speed compressor. Universidad de Castilla-La Mancha José Antonio Almendros Ibáñez. 265-275. http://hdl.handle.net/10251/180707S26527

Desarrollo de un sistema de seguridad frente a fugas de gases inflamables para el laboratorio del área térmica del IUIE

[ES] A raíz de la aceptación del protocolo de Montreal, en el cual se prohibieron gran parte de refrigerantes ampliamente utilizados, se está experimentado con refrigerantes alternativos entre los cuales destacan hidrocarburos como el propano. Esta memoria describe el diseño de un sistema de seguridad que detecte concentraciones peligrosas de propano y actúe en consecuencia activando procedimientos de alarma, ventilación, desactivando fuentes de ignición y notificando. El sistema se ha implementado en el laboratorio del Instituto Universitario de Ingeniería Energética (IUIE), funciona como elemento de seguridad para las personas que trabajan en él y consta de los siguientes elementos, los cuales se detallan en profundidad en esta memoria: - Sensores de detección de Propano - Autómata de lógica programable - Panel de notificaciones de alarma - Sistema de ventilación y extracción de gases - Modulo con conexión Ethernet para notificaciones a distancia[CA] Arran de l’acceptació del protocol de Montreal, al qual es van prohibir gran part dels refrigerants tradicionals àmpliament emprats, s’està experimentant amb refrigerants alternatius entre els quals cal destacar hidrocarburs com el propà. Aquesta memòria descriu el disseny de un sistema de seguretat que detecta concentracions perilloses de propà i actua en conseqüència notificant, activant procediments d’alarma, ventilació y desactivant fonts d’ignició. El sistema s’ha implementat al laboratori de l’Institut Universitari d’Ingenieria Energètica (IUIE) i funciona com a element de seguretat per a les persones que en ell treballen i consta dels següents elements els quals seran detallats al llarg d’aquest document: - Sensors de detecció de propà - Autòmat de lògica programable - Panell de notificacions d’alarma - Sistema de ventilació i extracció de gasos - Mòdul amb connexió Ethernet per a notificar a distància[EN] As a result of the acceptance of the Montreal protocol, in which much of the widely used refrigerants were banned, systems with alternative refrigerants have been developed. Among these alternative refrigerants hydrocarbons such as propane stand out. This report describes the design of a safety system that detects dangerous propane concentrations and acts accordingly by notifying, activating alarm procedures, ventilation, and disabling sources of ignition. The system has been implemented in the laboratory of the Universitary Institute of Energy Engineering (IIE), and works as a safety element for the people who work in it and consists of the following elements, which are detailed in depth in this report: - Propane sensors. - PLC. - Alarm display front panel. - Gas extraction system. - Module with Ethernet connection for remote notifications.TFG

Étude du débit de circulation de l'huile dans un compresseur à spirales à vitesse variable fonctionnant au propane

[EN] The use of hydrocarbons as refrigerants is being more common in recent years. Nevertheless, the solubility of propane in POE oils is significantly higher than in HFCs. This fact has made that POE oils used with hydrocarbons usually have a higher viscosity than the commonly used with HFCs. This approach solves the lubrication problem in the compressor but the way in which oil could affect the system performance is not so widely studied. In this work, an experimental analysis about the oil circulation rate of a variable speed compressor working with propane has been done. The study has analysed the oil circulation at different compressor speeds and evaporating temperatures. The obtained results have shown that the oil circulation rate increases with the compressor speed and reaches values higher than 5% at high speeds. This fact can penalize the COP of the system in more than 15% in these working conditions.The authors would like to acknowledge the Spanish "Ministerio De Economia Y Competitividad", through the project ref-ENE2017-83665-C2-1-P "Maximizacion de la eficiencia y minimizacion del impacto ambiental de bombas de calor para la descarbonizacion de la calefaccion/ACS en los edificios de consumo casi nulo" for the given support. In addition, Ruben Ossorio would like to thanks to the Spanish government his PhD scholarship PRE2018-083535.Ossorio-Santiago, RJ.; Navarro-Peris, E. (2021). Study of oil circulation rate in variable speed scroll compressor working with propane. International Journal of Refrigeration. 123:63-71. https://doi.org/10.1016/j.ijrefrig.2020.12.002637112