Theoretical and numerical analysis of a heat pump model utilizing Dufour effect

A heat pump model utilizing the Dufour effect is proposed and studied by numerical and theoretical analysis. Numerically, we perform MD simulations of this system and measure the cooling power and the coefficient of performance (COP) as figures of merit. Theoretically, we calculate the cooling power and the COP from the henomenological equations describing this system by using the linear irreversible thermodynamics and compare the theoretical results with the MD results.Comment: 13 pages, 16 figures(10 captions), published versio

Simulation of a heat pump model using SIMAN

A Heat pump is a system that follows the vapor compression cycle in which a vapor is compressed, then condensed to a liquid, following which the pressure is dropped so that fluid can evaporate at a low pressure. The system is considered to be a continuous system as there is a refrigerant whose state changes continuously throughout the system. This thesis work presents the application of the Simulation program SIMAN in a continuous modeling environment. The Refrigeration cycle was chosen as the Heat Pump as there is a continuous flow of the refrigerant through the system and hence was an excellent system for a continuous simulation problem. The Variables in the Heat Pump model were written as State variables in Fortran and was linked with SIMAN and the whole process was then controlled by the SIMAN processor

An air source heat pump model for operation in cold humid environments

There is considerable interest in the use of heat pumps as a potential low-carbon alternative to fossil fuel-based domestic space heating and hot water systems. In many cases, heat pumps are combined with other energy sources such as solar thermal and/or electric resistive heating, to ensure that building thermal loads can be met, and in order to minimise carbon emissions from such integrated systems. Whilst meeting the comfort demands in the occupied space, relatively complex control strategies are required in comparison to simple thermostatic control typically implemented to control gas fired heating systems in domestic buildings. Well characterised models of the principal components of these systems are required to explore and identify the most appropriate strategies in simulation. However, models of air source heat pumps (ASHPs) operating in humid climates, such as the UK, are limited. This paper presents an experimental setup designed to capture the operation of the ASHP in conditions similar to those found throughout a typical heating season in the UK. Results from a number of tests on a 10kW ASHP are presented in terms of the coefficient of performance (COP) and the steady-state operation are used to develop a model using empirical curve fitting. The overall maximum time constant is also established. The resulting model calculates COP as a function of air humidity, air temperature on the evaporator side and water temperature on the condenser side

Dual source solar assisted heat pump model development, validation and comparison to conventional systems

This paper presents a new SAHP system integrated with hybrid photovoltaic/thermal panels (PVT). The main components of the system developed are a dual-source HP, PVT panels and two storage tanks. The use of two storage tanks allows to directly store the hot water for DHW if water temperature reaches the set-point or to send it to the cold storage. On the other side, the use of two heat exchangers on source side, allows the system to switch from air to the cold tank increasing system’s performances. In this work the developed system is compared with two conventional systems: an AWHP integrated with standard photovoltaic panels and an AWHP integrated with hybrid PVT panels for DHW production only. Those systems were investigated for a single family house, through one year simulation in the TRNSYS software. Control strategy, size of the tanks and number of panels were investigated with parametric studies. Thanks to the good results of the simulations, an experimental prototype has been designed and built. Data observed from first monitoring campaign highlighted better performances than expected. After a season of investigation and data analysis for the system, new findings will be illustrate

Simplified modelling of air source heat pumps producing detailed results

Created by the Building Research Establishment (BRE), the Standard Assessment Procedure (SAP) is the UK Government‟s recommended method of assessing the energy ratings of dwellings. Modelling future complex dwellings, and their servicing systems, will require a more advanced calculation which is as simple as SAP to use but can produce more detailed results. This paper extends a novel advanced dynamic calculation method (IDEAS – Inverse Dynamics based Energy Analysis and Simulation) of assessing the controllability of a building and its servicing systems. IDEAS produces SAP compliant results and allows confident (i.e. calibrated in SAP) predictions to be made regarding the impact of novel heating and renewable energy systems. This paper describes the addition of an Air Source Heat Pump (ASHP) model to IDEAS. This allows for detailed analysis to be made of ASHPs in a SAP compliant framework. The benefits of using the IDEAS method is highlighted with capabilities outwith the scope of SAP also possible. For example, IDEAS can be used as sizing tool for a heating system in a building

Modelica-based Heat Pump Model for Transient and Steady-State Simulation Using Low-GWP Refrigerants

Due to the relatively high global warming potential (GWP) value of R410A, much effort has been devoted to the exploration of potential refrigerants to replace R410A in the heat pump applications. Those studies involving natural refrigerants, which are of zero or single-digit GWP values, have not yet demonstrated the readiness for the substitution because of various reasons such as low cycle efficiency, toxicity and flammability. Henceforward, some synthetic refrigerants whose GWP values are significantly lower than R410A such as R32 and some R32-based blends such as D2Y60, are getting more attention. To evaluate the transient performance of those low-GWP refrigerants, a Modelica-based heat pump model is developed to simulate a heat pump cycle during both steady state operations and transient operations. The model includes an efficiency-based compressor model, two segmented heat exchanger models, a control volume-based valve model and segmented pipe models. The heat exchanger model is capable of simulating multi-bank multi-circuit tube-fin heat exchangers with an arbitrary number of segments. The pipe model is developed based on the segmented heat exchanger model, and its implementation provides for better charge prediction compared to single lump model. In order to speed up the simulations, accelerated refrigerant property routines were developed for R32 based on REFPROP. System-level steady-state and transient simulations for several alternative low-GWP working fluids, R32 and D2Y60, are conducted. The simulation results are compared with the published experimental data obtained from the Alternative Refrigerant Evaluation Program (AREP). The data includes steady-state operation data based on ASHRAE A, B and C tests, and transient data from ASHRAE D cyclic operation test. The validation of R32 and D2Y60 steady-state data shows a maximum deviation of 7.5% and an average deviation of 4%. The transient simulation well captures the dynamic performance of vapor compression cycle during start-up and shut-down

Sub-hourly simulation of residential ground coupled heat pump systems

Residential Ground Coupled Heat Pump systems are usually characterised by an ON/OFF behaviour of the heat pump with typical cycling frequencies of 1 - 4 cycles per hour. The ground loop fluid pump has the same ON/OFF behaviour and the borehole heat exchanger operates either in full flow or no flow conditions. Typical hourly simulations of GCHP systems use steady-state models for the heat pump and the borehole fluid (transient models being used for buildings and heat transfer in the ground). This paper reviews the models used in typical hourly simulations as well as transient models that are available and compares the results obtained using the two classes of models within the TRNSYS simulation environment. Both the long-term energy performance and the optimum system design are compared. It is shown that using steady-state models leads to an overestimation of the energy use that ranges from a few percents with oversized borehole heat exchangers to 75% for undersized exchangers. A simple Life Cycle Cost analysis shows that using steady-state models can lead to selecting a very different design than the one that would have been selected using dynamic models

T-Shape Molecular Heat Pump

We report on the first molecular device of heat pump modeled by a T-shape Frenkel-Kontorova lattice. The system is a three-terminal device with the important feature that the heat can be pumped from the low-temperature region to the high-temperature region through the third terminal. The pumping action is achieved by applying a stochastic external force that periodically modulates the atomic temperature. The temperature, the frequency and the system size dependence of heat pump are briefly discussed.Comment: 6 figure