In situ optimization methodology for the water circulation pumps frequency of ground source heat pump systems

[EN] This paper presents an experimental study of the influence of the water circulation pumps frequency atthe indoor and outdoor loops in the overall system performance of a ground source heat pump moni-tored plant, and describes a three steps new methodology to optimize the system energy performanceand obtain the values of the optimal frequencies when ON/OFF regulation is employed. The first stepconsists of several experimental tests of pseudo-random sequence of frequency steps for both, internaland external circulation pumps, carried out during a single day. The second step is the characterization ofthe quasi-steady state system performance as a function of circulation pumps frequencies. The final stepconsists of, by means of an analytical expression, the extrapolation of results to any partial load ratio,what allows finding the optimal frequency as a function of the instantaneous thermal load. The advantageof the proposed methodology is that it can be carried out on site and is able to consider the phenomenaoccurring at the heat pump and the ground source heat exchanger when the flow rates are varied. Themethodology can be applied to any installation incorporating variable speed circulation pumps. Resultsindicate large energy savings potential for this kind of installation.This work was supported by the European Commission under the FP7 framework project GROUND-MED: "Advanced ground source heat pump systems for heating and cooling in Mediterranean climate".Montagud Montalvá, CI.; Corberán Salvador, JM.; Montero Reguera, ÁE. (2014). In situ optimization methodology for the water circulation pumps frequency of ground source heat pump systems. Energy and Buildings. 68, A:42-53. https://doi.org/10.1016/j.enbuild.2013.09.030S425368,

Seasonal performance assessment of sanitary hot water production systems using propane and CO2 heat pumps

[EN] This paper presents an experimental analysis and performance evaluation of a ground source heat pumpsystem providing heating/cooling to an office building, located at the Universitat Politècnica de Valènciain Spain. The experimental data and a detailed description of the analysis tool used were presented ina previous paper for the first six operational years. This paper provides the adaptation of such analysistool to the new configuration (heat pump with two compressors working in tandem), and provides anupdated complete reference data sets over more than eleven years which can be used by researchers formodel validation purposes.The work of M. Tammaro on electric heat pumps is supported by the Next Heat Pump Generation project (funded by the European Commission in the 7th Framework Programme, grant number 307169 - European Heat Pump Association, 2013), which is gratefully acknowledged.Tammaro, M.; Montagud, C.; Corberán, J.; Mauro, A.; Mastrullo, R. (2017). Seasonal performance assessment of sanitary hot water production systems using propane and CO2 heat pumps. International Journal of Refrigeration. 74:222-237. https://doi.org/10.1016/j.ijrefrig.2016.09.0262222377

In situ optimization methodology for the water circulation pumps frequency of ground source heat pump systems: Analysis for multistage heat pump units

[EN] In order to optimize the global energy performance of a ground source heat pump system, special attention needs to be paid to the auxiliaries as they stand for a considerable part of the total energy consumption. A new in situ experimental methodology based on the frequency variation of the water circulation pumps in order to optimize the energy performance of the system was previously published by the authors for a ground source heat pump system using a single stage heat pump with ON/OFF regulation. The original single stage heat pump was recently replaced with a multistage unit consisting of two compressors of the same capacity working in tandem. A new experimental campaign was carried out and a new study was performed in order to adapt the in situ optimization methodology to the performance of the tandem compressors unit, and, by extension, to the multistage case. This paper presents the in situ optimization methodology for the water circulation pumps frequency adapted for multistage ground source heat pump systems. Results show that energy savings up to 32% can be obtained by applying this optimization methodology.This work was supported by the "Programa de Ayudas de Investigacion y Desarrollo (PAID)" of the Universitat Politecnica de Valencia. This work was also supported by the European FP7 project "Advanced ground source heat pump systems for heating and cooling in Mediterranean climate" (GROUND-MED).Cervera Vázquez, J.; Montagud Montalvá, CI.; Corberán Salvador, JM. (2015). In situ optimization methodology for the water circulation pumps frequency of ground source heat pump systems: Analysis for multistage heat pump units. Energy and Buildings. 88:238-247. https://doi.org/10.1016/j.enbuild.2014.12.008S2382478

Analysis of the energy performance of a ground source heat pump system after five years of operation

[EN] GeoCool plant was the result of a EU project whose main purpose was to adapt ground coupled heat pump technology to coolingdominatedareas. The executionofthis experimentalplant was completedatthe end of year 2004, starting on February 2005 the regular operation of the air conditioning system. Since then, GeoCool facility has been monitored by a network of sensors characterizing its most relevant parameters. Several aspects of the performance and behaviour of the system during its first operational year were presented on a previous paper. This paper presents the energy performance measurements of GeoCool ground coupled heat pump system acquired during five years of operation as well as the evolution of the return water temperature from the ground as a representative of the ground temperature. The analysis of the experimental results shows that the system energy performance is maintained through the years with no appreciable impact on ground thermal responseThis work has been supported by FP7 project "Advanced ground source heat pump systems for heating and cooling in Mediterranean climate" (GROUND-MED).Montagud Montalvá, CI.; Corberán Salvador, JM.; Montero Reguera, ÁE.; Urchueguía Schölzel, JF. (2011). Analysis of the energy performance of a ground source heat pump system after five years of operation. Energy and Buildings. 43(12):3618-3626. https://doi.org/10.1016/j.enbuild.2011.09.036S36183626431

Oil sump temperature in hermetic compressors for heat pump applications

The oil temperature in the compressor sump is an important parameter describing the performance of a refrigeration compressor. Its estimation is necessary for evaluation of the lubricant-refrigerant mixture composition and its properties. In contrast, this temperature is not normally measured in compressor performance tests and is unlikely reported by the manufacturers or in the technical literature. In this paper, a set of tests measuring the oil sump temperature for hermetic reciprocating and scroll compressors in a wide range of working conditions is presented. From these results and after a theoretical analysis of the factors having influence on this parameter, a correlation for the oil temperature as a function of compressor inlet and outlet conditions is presented. This correlation allows to estimate the oil sump temperature for scroll and hermetic reciprocating compressors as a function of operation conditions with an error lower than 4 K degree for most of the cases.This work has been partially funded by the Spanish Ministerio de Ciencia e Innovacion through project, ref. DPI 2008-06707-C02-01 (Estudio de optimizacion de equipos frigorificos de aire acondicionado para su funcionamiento con refrigerantes naturales (hidrocarburos)).Navarro-Peris, E.; Corberán Salvador, JM.; Martínez Galván, IO.; Gonzálvez Maciá, J. (2012). Oil sump temperature in hermetic compressors for heat pump applications. International Journal of Refrigeration. 35(2):397-406. https://doi.org/10.1016/j.ijrefrig.2011.10.006S39740635

Sizing of a reversible magnetic heat pump for the automotive industry

[EN] This paper focuses on the design of an innovative air-conditioning system, namely a magnetocaloric air-conditioner for an electric minibus. An integrated design of the complete system is necessary, as the hot and cold side of the regenerator will work under dynamic conditions which depend on the instantaneous thermal load in the cabin. In order to assist the design of the system, a dynamic model has been developed for the cabin, the hydraulic loops and heat exchangers, and the magnetocaloric unit. This paper presents (i) a description of the dynamic models, (ii) an analysis of the operating conditions of the magnetocaloric unit and (iii) a discussion on the design of the magnetocaloric air-conditioner. The results show that the electric minibus requests 1.60 kW of cooling power over a span of 37 K in cooling mode, and 3.39 kW of heating power over a span of 40 K.This work has been supported by the European Commission under the 7th European Community framework program as part of the ICE project "MagnetoCaloric Refrigeration for Efficient Electric Air-Conditioning", Grant Agreement no. 265434. B. Torregrosa-Jaime acknowledges the Spanish Science and Innovation Ministry (Ministerio de Ciencia e Innovacion) for receiving the Research Fellowship FPU ref. AP2010-2160.Torregrosa Jaime, B.; Corberán Salvador, JM.; Vasile, C.; Muller, C.; Risser, M.; Payá Herrero, J. (2014). Sizing of a reversible magnetic heat pump for the automotive industry. International Journal of Refrigeration. 37:156-164. https://doi.org/10.1016/j.ijrefrig.2013.06.018S1561643

Partialization losses of ON/OFF operation of waterto- water refrigeration/heat-pump units

[EN] This paper presents the results of an experimental campaign for the characterization of the dynamic behavior of a water-to-water refrigeration/heat-pump unit under ON/OFF operation. The unit was previously tested at different water inlet temperatures under steady state conditions, and a very good agreement was found between the instantaneous dynamic performance of the heat pump and the corresponding quasi-steady state operation. In parallel, a series of tests were carried out to quantify the coefficient of performance (COP) degradation as a function of the load ratio, and a simple formula for the Part Load Factor is presented. Results lead to the conclusion that the only non-negligible factor in the COP degradation is the stand-by electrical consumption during the OFF period, especially at low load ratios. Finally, it is concluded that the minimization of the stand-by consumption is a key point for the future improvement of the seasonal performance of water-to-water systems.This research has been partially funded by the European FP7 framework project "Advanced ground source heat pump systems for heating and cooling in Mediterranean climate" (GROUND-MED) and the Spanish Ministry of Economy and Competitiveness (MINECO) through the project "Estudio de evaporadores y condensadores basados en tecnologia de minicanales para su aplicaciOn en equipos de aire acondicionado, refrigeraciOn y bomba de calor estacionarios" with reference DPI2011-26771-C02-01. The authors gratefully acknowledge their financial support.Corberán, JM.; D.Donadello; Martínez Galván, IO.; Montagud, C. (2013). Partialization losses of ON/OFF operation of waterto- water refrigeration/heat-pump units. International Journal of Refrigeration. 36(8):2251-2261. https://doi.org/10.1016/j.ijrefrig.2013.07.002S2251226136

Experimental validation of a short-term Borehole-to-Ground (B2G) dynamic model

[EN] The design and optimization of ground source heat pump systems require the ability to accurately reproduce the dynamic thermal behavior of the system on a short-term basis, specially in a system control perspective. In this context, modeling borehole heat exchangers (BHEs) is one of the most relevant and difficult tasks. Developing a model that is able to accurately reproduce the instantaneous response of a BHE while keeping a good agreement on a long-term basis is not straightforward. Thus, decoupling the short-term and long-term behavior will ease the design of a fast short-term focused model. This work presents a short-term BHE dynamic model, called Borehole-to-Ground (B2G), which is based on the thermal network approach, combined with a vertical discretization of the borehole. The proposed model has been validated against experimental data from a real borehole located in Stockholm, Sweden. Validation results prove the ability of the model to reproduce the short-term behavior of the borehole with an accurate prediction of the outlet fluid temperature, as well as the internal temperature profile along the U-tube.The present work has been supported by the FP7 European project "Advanced ground source heat pump systems for heating and cooling in Mediterranean climate" (GROUND-MED), and by the "Resource-Efficient Refrigeration And Heat Pump Systems" (EFF-SYS+) program.Ruiz Calvo, F.; Rosa, MD.; Acuña, J.; Corberán Salvador, JM.; Montagud Montalvá, CI. (2015). Experimental validation of a short-term Borehole-to-Ground (B2G) dynamic model. Applied Energy. 140:210-223. https://doi.org/10.1016/j.apenergy.2014.12.002S21022314

A propane water-to-water heat pump booster for sanitary hot water production: Seasonal performance analysis of a new solution optimizing COP

[EN] Electrical heat pumps for sanitary hot water production achieve a high performance with a good matching of water and refrigerant temperature profiles during the heat rejection stage, as it happens in CO2 systems. This work considers the thermodynamic possibility to adapt the condenser pressure of a propane heat pump to maximize the COP, while producing sanitary hot water up to 60 C from a heat sink equal to 15 or 25 C. The performance of the heat pump is calculated through specific models which, in combination with a TRNSYS model of the whole system, allowed to assess its seasonal performance for a hotel in Strasbourg, also varying the control logic and the size of the storage tank. Results obtained led to the conclusion that, for achieving a high seasonal performance, the control logic of the tank has the largest influence.Part of the results of this study were developed in the mainframe of the FP7 European project ‘Next Generation of Heat Pumps working with Natural fluids’ (NxtHPG). Part of the work presented was carried by M. Tammaro during his visit at the Instituto de Ingenierı´a Energetica, Universitat Politecnica de Val encia and by C. Montagud during her visit at the Department of Industrial Engineering, Federico II University of Naples, with the financial support of the POLIGRID project.Tammaro, M.; Montagud Montalvá, CI.; Corberán Salvador, JM.; Mauro, AW.; Mastrullo, R. (2015). A propane water-to-water heat pump booster for sanitary hot water production: Seasonal performance analysis of a new solution optimizing COP. International Journal of Refrigeration. 51:59-69. https://doi.org/10.1016/j.ijrefrig.2014.12.008S59695

In situ optimization methodology for ground source heat pump systems: Upgrade to ensure user comfort

[EN] Ground source heat pump systems have been proved to be one of the most efficient systems for heating and cooling in buildings. However, an optimal energy performance depends on a good control of the auxiliaries, which stand for an important part of the total energy consumption. The authors previously developed an experimental in situ optimization methodology for the water circulation pumps frequency of ground source heat pump systems when single stage and multi-stage ON/OFF regulation is employed. However, the user comfort was not completely met under extreme weather conditions during summer. This paper presents the upgrading of this energy optimization strategy combining circulation pumps frequency variation and building supply temperature compensation in order to ensure the user comfort while keeping high energy savings. Experimental results show that the user comfort is met by means of this new methodology and the energy savings (33%) are even higher than those obtained with the previous methodology. (C) 2015 Elsevier B.V. All rights reserved.This work was supported by the "Programa de Ayudas de Investigacion y Desarrollo (PAID)" of the Universitat Politecnica de Valencia. This work was also supported by the European FP7 project "Advanced ground source heat pump systems for heating and cooling in Mediterranean climate" (GROUND-MED).Cervera Vázquez, J.; Montagud Montalvá, CI.; Corberán Salvador, JM. (2015). In situ optimization methodology for ground source heat pump systems: Upgrade to ensure user comfort. Energy and Buildings. 109:195-208. https://doi.org/10.1016/j.enbuild.2015.10.026S19520810