Abstract
The energy efficiency of air-to-water heat pump operating in an actual heating installation depends on many factors. In order to create a reliable model of the unit, it is necessary to include as many of them as possible. Unfortunately, the most common data provided by heat pump manufacturers are based on tests performed in accordance with the EN 14511 standard [1]. These tests are performed in steady-state conditions and do not provide reliable information on the impact of dynamic effects on the energy efficiency of the device. The solution may be the tests in quasi-dynamic conditions. The article presents the possibility of creating the characteristics of an air-to-water heat pumps based on operational data. The accuracy of the created model has been compared with the characteristics resulting from measurements in steady state conditions. It has been confirmed that dynamic test data, after proper selection, will allow to determine the characteristics of repeatable parameters and this can be an alternative to tests performed in fixed conditions.
Highlights
The heating power and the coefficient of performance (COP) of air-to-water heat pumps are influenced by many factors
The basis for the calculation of the instantaneous COP value and the heating power (QHP) is data provided by the heat pump manufacturer, which is based on tests performed in accordance with the EN 14511 [1] standard
The COP value relative to the declared value (COPd) value determined on the basis of these tests concerns only the situation when the heat pump works at full heating load in the active cycle
Summary
The heating power and the coefficient of performance (COP) of air-to-water heat pumps are influenced by many factors. The basis for the calculation of the instantaneous COP value and the heating power (QHP) is data provided by the heat pump manufacturer, which is based on tests performed in accordance with the EN 14511 [1] standard. At the moment, this is the most accurate and common source of information for the purpose of air-to-water heat pumps work simulations. The main problems concern: insufficient number of measuring points (e.g. no data for inlet temperature below 35°C), constant temperature difference on the condenser (5 K), no evaluation of the frequency inverter influence on the COPd and heating power of the device, as well as the lack of evaluation of the partial load effect and the way of the device’s power adjustment to its efficiency. Corrections to take into account the effect of these dynamic conditions on the efficiency of the heat pump are taken into account [5–8]
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