Global issues of greenhouse gas emissions, security of supply and decreasing fossil fuel resources calls for increased use of renewable energy and energy efficiency measures for existing technology. In the domestic sector, main energy consumption occurs due to space heating and hot water which is mostly provided by gas or oil boiler via hydronic central heating system in the UK. In order to diversify fossil fuel usage, reduce emissions and security supply, implementation of efficient technology (e.g. heat pump) along with renewable technology is vital. The heat pump is an efficient technology based on the vapour compression cycle, mostly driven by electric motors where it provides heat at high temperature by consuming energy from low temperature sources such as air, ground or water. Electric heat pumps (EHPs) have good potential to displace existing gas boiler system to meet domestic heating demand. However, conventional hydronic systems operate with high flow temperatures where EHP's performance drops as temperature lift increases. In addition, if vast deployment of EHPs occurs then it could create issues for the electricity distribution network. Also, until the major portion of electricity is generated by renewable sources, EHP's operating at high temperatures will not give significant benefit in terms of C02 savings compared gas boiler heating. The aim of the presented work is to develop an engine driven heat pump system. This will meet the designed domestic heat demand at high flow temperatures suitable for conventional wet radiator systems. It will also use the waste heat recovered from the engine. The developed engine driven heat pump (ENHP) should also help in diversification of fossil fuel usage in domestic sector, emission reduction and thermal comfort improvement. Liquid biofuels or gas engine concepts will be possible at a later date. The diesel engine was used with modifications to take advantage of coolant and exhaust heat recovery. The engine was coupled with a reciprocating open compressor as a drive source. A water-to-water heat pump was developed for testing purposes. Diesel engine heat pump (DEHP) performance was tested at three different engine speeds and four different water flow temperatures for given evaporation temperature conditions. DEHP test results showed a strong influence of engine speed and condensing temperature on overall total heat output and heat recovery. Test results showed that heat recovery from the engine contributes about 31 % in total heat output. DEHP test results at various conditions gave primary energy ratio in a range of 0.93 to 2 showing better performance compared to conventional gas boiler. Speed variation of the DEHP system showed that it has the potential to match domestic heating demand ( at 70-73 0 C) between -4.5°c to 9°C air/water temperature by varying engine speed, hence reduction in on/off cycling. In terms of flow temperature requirements for retrofit application, the DEHP test results showed that it can provide flow temperatures in the range of 70°C to 73°C which is in a similar range of gas boiler flow temperature range in a typical household. In addition, DEHP system can provide water flow rate in a range of 5 to 20 lImin which is suitable to meet typical space heating and/or DHW flow rate demand. Another common issue was noise associated with the DEHP system and this was also reduced by acoustic insulation around the engine-compressor assembly showing potential for domestic installation where noise and vibration could be achieved in a similar range to conventional heating system. Overall, DEHP test results showed potential as a transition retrofit technology with possible use of renewable energy sources (e.g. biofuel) with integration of thermal/electrical energy storage to meet heating and electricity demand locally.

This work presents a method to improve the prediction accuracy of a meanline modelling approach for automotive turbocharger style centrifugal compressors. This has been achieved using a novel active flow zone theory which has been combined with an existing single zone meanllne modelling technique and an existing collection of loss models. The work begins by identifying the weaknesses in the existing meanline modelling techniques available in open literature before identifying single zone modelling as being the most suitable platform for further impeller modelling improvements. During the development of the meanline modelling technique three turbocharger compressor datasets were provided by IHI Charging Systems International for analysis. The various loss model collections available in open literature were then benchmarked and a particular set of loss models was identified as being the most robust and providing the best performance prediction accuracy for the compressors of interest. With all of tile mean line modelling techniques and loss model collections assessed accuracy was always lost toward surge and at high tip speeds. The test data always showed a flattening of the pressure ratio characteristic curve for a fixed speed toward surge to an extent that the pressure ratio effectively remains constant. It was hypothesised that impeller inlet recirculation was driving this performance toward surge and therefore this was investigated using a single passage 3D CFD model. Using the data collected from the CFD simulations for the compressors it was shown that the scale of the impeller inlet recirculation varies predictably across a range of operating conditions and compressors, for this reason a correlation was developed to represent this. The variation of the inlet flow conditions were Investigated in the same fashion and it was discovered that they too varied predictably; correlations were developed at the impeller inlet for the size of the recirculating zone, the active flow total temperature, and the active flow circumferential component of velocity. Based on the data collected from the CFD a novel concept for impeller work input was suggested whereby the active flow zone is the only part of the Impeller contributing to pressure rise; this is the basis for the novel mean line modelling technique which is described in this document. The new method was shown to provide improved performance prediction accuracy toward surge as targeted, All of the modelling techniques were then bencl1marked further using two additional compressors provided by the industrial sponsor, Detailed inter-stage pressure measurements are presented at the impeller leading and trailing edge and the weaknesses in all of the modelling methods used are exposed with the aim of inspiring future work,

No description available.

No description available.

Surge is a system instability related to interaction between the compressor, the ducting and the throttle in a given compression system. This limit is critical for automotive turbochargers as it dictates the minimum flow rate of the internal combustion (IC) engine. The inlet valve train of the IC engine cylinder arrangement influences the operation of a turbocharger compressor. It is this valve motion that sets a pulsating exit state for the compressor and, as such, it can impose a further limit on the compressor operation range limiting further the engine minimum flow rate. This thesis presents an experimental evaluation of the surge dynamics on a compressor with induced downstream pulsating flow. Different pulsation levels will be characterized by means of the frequency and amplitude of the pulse. Multiple experiments are carried out in a purpose-built test bench that has components similar to a turbocharger engine system: compressor, duct, plenum and throttle. Experimental data will be presented for a range of frequencies, amplitudes at a given compressor speed, and the effect of these parameters will be analysed independently. The main effect on the surge margin of the compressor has been found to be due to the presence of a volume in the system for all cases, whether steady or pulsating condition, and at all frequencies. It was found that the magnitude of the pulse frequency determines the hysteresis behaviour of the system that leads to a phase difference between the convected terms (volume flow) and the acoustic dominated terms (pressure), and therefore this affects the onset of flow instability, surge, in the compression system under study. Based on these results, the compressor performance, and particularly its stability limit, is strongly influenced by the downstream conditions of the system where the compressor is placed.

Tens of thousands of centrifugal compressors are installed worldwide in chemical and petrochemical plants. The performance of these compressors degrade during the operation as a consequence of effects such as fouling, erosion, corrosion, and abrasion. A performance monitoring method that could detect and assess the magnitude of the degradation would be greatly beneficial to schedule production and maintenance leading to an economic profit for the operation. After searching the literature, it was concluded that such a method is yet to be developed for industrial centrifugal compressors. This thesis shows the development of an adaptive monitoring framework that simultaneously considers the degradation of the state of health and identifies the malfunctioning of sensors. Indeed, because of degradation, the state of the components changes over time and this change can be observed in the measurements, however, the measurements are also affected by random or persistent errors. The approach adopted in this thesis aims at reconciling two distinct features that are normally separated: (1) to account for the degraded state by recursively matching the model to the newly available measurements, and (2) to correct the measurements when these are biased by making use of the model. The leading hypothesis is that this aim can be achieved by employing models that establish causality relationships between the state of the components and the measured variables together with mathematical optimization methods. The thesis demonstrates: how performance can be systematically modelled even though a compressor is installed at the industrial site, how the degradation of performance can be detected and quantified in real-time, and finally, how the effects of degradation on performance can be modelled and monitored while simultaneously detecting and correcting sensor faults. The methods have been successfully applied to a 10 MW centrifugal compressor. When monitoring and modelling the degradation of its performance, it was observed that the difference between the performance of the compressor in undegraded and degraded state depends on the operation conditions. The implication of this observation is that the state-of-the-art practice of scaling the manufacturer maps to obtain degraded maps can lead to misleading conclusions about the performance of the degraded compressor.

No description available.

The use and application of compressors cannot be overemphasized in the aeronautical and oil & gas industries. Yet research works in sufficient depth has not been conducted previously to analyze their actual behaviour under degraded or even new conditions in operation. For the purpose of degradation modeling and simulation, a compressor model was set up using thermodynamic equations and affinity laws representing the characteristics of a clean compressor. HYSYS was used for degradation modeling analysis by implanting known linear and nonlinear degradation trends for an operating point and taking the compressor measurement changes. It was then assumed the degradation levels are unknown and these were established by applying the compressor health indices to the new compressor map. A diagnostic method for compressors was developed where the prediction in degradation levels were compared for diagnostic purposes. By applying a unique “successive iteration method” to a real gas site compressor data at various speeds, a compressor performance adaptation technique has been developed in this thesis which maps out the actual performance of the compressor shows the errors in performance prediction has been reduced from 5-15% to a minimum. This performance adaptation method allows the compressor performance map to be adapted against field data of a compressor for a range of speeds. All data were corrected to a common datum and GPA Indices were utilised for the evaluation of confidence in the established method. By observing the centrifugal compressor performance data from 2006 to 2010, the actual compressor degradation was quantified and modeled by trending techniques for diagnostic and prognostic purposes so that the operator can plan ahead for maintenance by knowing an estimate for the actual health of the compressor at any time. The major conclusions are that the performance adaptation developed for the site compressor and the diagnostic technique by data trending has been successful. And estimation of degradation in health indicators (throughput, pressure ratio and efficiency drops) by scaling the measurable parameters is a useful tool for diagnostic purposes.

In low temperature processes, such as natural gas liquefaction, refrigeration and power systems are highly interacted with each other through mechanical power consumption and supply. Shaft power consumption of a refrigeration process has a significant impact on equipment selection for a power system. Such influences are eventually passed on and dramatically affect the overall fuel consumption of the power system, which represents a large proportion of operation cost in low temperature processes. This research has been devoted to exploit the interactions between refrigeration and power systems, and develop systematic design methodologies for both refrigeration and power systems. For refrigeration system synthesis, novel refrigeration processes have been proposed to balance the performance between shaft power consumption and process structural complexity. For each refrigeration process, a generic algorithm has been applied to identify the best operating conditions. Although the global optimality can not be guaranteed due to the highly non-linear nature of this problem, greater confidence in solution optimality can be achieved with the adoption of a stochastic optimisation method. With new design variables introduced in these novel refrigeration processes, more flexible condition selection for refrigeration evaporation can be achieved. Thus, more opportunities for cycle efficiency improvement can be exploited.

A growing global environmental awareness and the rising costs of energy are driving demand for the development of sustainable cooling technologies. Most governments worldwide have implemented minimum energy performance standards for household refrigerators and innovative new solutions are required to improve the efficiency of these appliances. This thesis investigated the design and operation of a thermal storage refrigerator. The aim was to improve the refrigerator energetic efficiency, temperature stability and extend its offcycle. The research demonstrated that larger displacement compressors are more efficient. The proposed method to exploit the superior performance of large compressors is to accumulate their high cooling capacity in a phase change material (PCM). The combination of thin phase change material with a large displacement compressor is a novel design approach with the potential to enhance the refrigerator efficiency. Theoretical modelling and experimental validation were undertaken to determine the phase change material charge and discharge rate and the corresponding refrigerator on and off cycle durations. The integration of a 5 mm PCM slab into the refrigerator allowed 3 to 5 hours of continuous operation without power supply (compared to 9 minutes without PCM) depending on the ambient temperature. A computational fluid dynamics (CFD) model was used to predict the airflow and temperature distribution within the thermal storage refrigerator. Several design options were investigated by simulation to identify the most effective PCM configuration (horizontal or vertical), the phase change temperature and the design for the refrigerator i.e. conventional door type or top opening drawer appliance. The CFD was used to select the best design options for developing a novel thermal storage refrigerator. A horizontal PCM configuration was found to be more efficient than a vertical PCM. The temperature distribution with a horizontal PCM was tested experimentally and the results were shown to be in close agreement with the CFD predictions. Both the simulation and the experimental results suggested that a eutectic with a phase change temperature below 0°C needs to be employed to maintain the compartment temperature within acceptable limits.