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Abstract The subcritical ORC (SCORC) is considered the industry standard due to its simple configuration, acceptable efficiency and low costs. However, it is known that alternative ORC configurations have the potential to increase efficiency. A cycle modification which closely resembles the SCORC is the partial evaporating ORC (PEORC), where a two-phase mixture of liquid-vapour enters the expander instead of superheated vapour. In theoretical studies at design conditions, higher power outputs are achieved for the PEORC compared to the SCORC. This work aims to go a step further by investigating the performance of the SCORC and PEORC under time-dependent operating conditions. A direct comparison between the SCORC and PEORC is made for identically sized systems using as input the waste heat stream of a waste incinerator plant and the changing ambient conditions. Performance maps of both cycle configurations are compiled and the benefit of an expander operating at variable speed is briefly discussed. The results indicate that for the specific case under investigation, the PEORC has an increased annually averaged net power output of 9.6% compared to the SCORC. Use of annually averaged input conditions results in an overestimation of the net power output for both the SCORC and PEORC, and furthermore, the relative improvement in power output for the PEORC is reduced to 6.8%. As such, the use of time-averaged conditions when comparing cycle architectures should preferably be avoided. [ABSTRACT FROM AUTHOR]

Abstract Organic Rankine cycle (ORC) engines in waste-heat recovery applications experience variable heat-source conditions (i.e. temperature and mass flow-rate variations). Maximising ORC system performance while accounting for off-design operation in response to such variations is of crucial importance for the financial viability and wider adoption of this technology. In this paper, the off-design performance of an ORC engine is investigated in a heat-recovery application from a stationary internal combustion engine (ICE), employing a screw expander and two heat exchanger (HEX) architectures. Unlike previous studies where the ORC expander and HEX performance are assumed fixed during off-design operation, here we consider explicitly the time-varying characteristics of these system components. Nominal system sizing results indicate that the screw expander isentropic efficiency exceeds 80%, and that the heat transfer area requirements of plate HEXs (PHEXs) are 50% lower than those of double-pipe HEXs (DPHEX). Following nominal system design, the ORC engine operation is optimised at conditions relating to part-load (PL) operation of the ICE. Although, the heat transfer coefficients in the evaporator decrease by 30% at PL, the HEX effectiveness increases by up to 20% due to higher temperature differences between the working fluid and the heat source, and the performance of the PHEX appears less sensitive to off-design operation conditions. The optimum PL screw expander efficiency maps reveal only a minor reduction of the expander efficiency (by 2%) relative to the design conditions. Optimum off-design maps indicate that the power output of the ORC engine reduces to 72% of full-load for an ICE at 60% of full-load, and that ORC engines with PHEXs generate slightly more power for the same heat-source conditions. Overall, the tool developed predicts ORC performance over an operating envelope and allows the selection of optimal HEX and expander designs. The findings can be used by ORC plant operators to optimise the ORC engine power output given varying on-site heat-source conditions, and by ORC vendors to inform HEX and expander design decisions. [ABSTRACT FROM AUTHOR]

In recent years, computational fluid dynamics (CFD) has been applied for the design and analysis of positive displacement machines (both compressors and expanders) with numerous challenges due to the dynamics of the compression (or expansion) process and deforming working chambers. The relative motion and in turn, the variation of the gaps during machine operation implies several obstacles for the implementation of reliable CFD models. The majority of the studies reported in literature focused on scroll, twin screw and reciprocating machines. The limitation of the developed methodologies to be applied directly to positive displacement machines with more complex meshing such as that of single-screw has been highlighted in literature. In this paper, a single screw expander is studied by means of (i) a moving mesh technique (dynamic mesh in the Key Frame Remeshing approach) and (ii) a real gas model of a R134a (Peng-Robinson model) implemented in OpenFOAM ®. On the top of that, all the possible techniques that come with the software are investigated in their application to single screw. An useful review of the state of the art CFD with open-source software (OpenFOAM-v1606+ and foam-extend4.0) is therefore carried out. The reliability of CFD model represents indeed the first step on which the design process and further optimization will be based. [ABSTRACT FROM AUTHOR]

There is significant interest in the deployment of organic Rankine cycle (ORC) technology for waste-heat recovery and power generation in industrial settings. This study considers ORC systems optimized for maximum power generation using a case study of an exhaust flue-gas stream at a temperature of 380 °C as the heat source, covering over 35 working fluids and also considering the option of featuring a recuperator. Systems based on transcritical cycles are found to deliver higher power outputs than subcritical ones, with optimal evaporation pressures that are 4-5 times the critical pressures of refrigerants and light hydrocarbons, and 1-2 times those of siloxanes and heavy hydrocarbons. For maximum power production, a recuperator is necessary for ORC systems with constraints imposed on their evaporation and condensation pressures. This includes, for example, limiting the minimum condensation pressure to atmospheric pressure to prevent sub-atmospheric operation of this component, as is the case when employing heavy hydrocarbon and siloxane working fluids. For scenarios where such operating constraints are relaxed, the optimal cycles do not feature a recuperator, with some systems showing more than three times the generated power than with this component, albeit at higher investment costs. [ABSTRACT FROM AUTHOR]

Positive displacement expanders are proven to be cost-effective in the low to medium power range for Organic Rankine Cycle (ORC) systems. Among the different types of volumetric expanders, the screw-type presents a favorable combination of relatively high internal volume ratio (up to 7) and isentropic efficiency (up to 80%) with respect to the optimal pressure ratio at which sub-critical ORCs operate. In particular, single-screw expanders have shown some potential due to their symmetric and balanced configuration that decreases the loads on the bearings. A comprehensive characterization of this type of machine with two working fluids, i.e., SES36 and R245fa, has been carried out in a previous work [1]. Based on the experimental work, friction losses and internal leakages were found detrimental to the expander performance. As the expander requires lubrication during operation, flooded expansion can be beneficial to reduce such losses as well as to improve the expansion process toward a quasi-isothermal behavior. A thermodynamic cycle model has been developed to evaluate the potential improvements on the thermodynamic performance of organic Rankine cycle with flooded expansion and internal regeneration. A semi-empirical model of the expander is included which accounts for the effects of internal volume ratio. The results from the cycle model have used to design an ORC test setup with an independent lubricant oil loop and internal regeneration. The new test rig will be used validate the trends obtained with the cycle model and to further characterize the single-screw expander. The working fluid employed is R1233zd(E) as a replacement for R245fa. [ABSTRACT FROM AUTHOR]

High efficiency expanders which can cope with fluid-vapour mixtures (i.e wet expansion) at the inlet and during expansion have the potential to increase the power output from thermodynamic power cycles. Volumetric expanders are considered suitable, yet experimental results are scarce and there is no model that can predict the performance of the expansion process. This is mainly due to the knowledge gap on the fundamental aspects off two-phase expansion and the non-equilibrium effects. Therefore, in this work, a variable volume piston expansion chamber is designed. The influence of the main design parameters are investigated by means of a simple deterministic model. Based on initial figures of merit, the component selection and technical layout is presented. The optical access in a later stage will be crucial to allow investigating the mechanistic process of the nucleation and the interfacial effects. This understanding is essential for generalization of the results to other working fluids and geometries. [ABSTRACT FROM AUTHOR]

Positive displacement expanders are proven to be cost-effective in the low to medium power range for Organic Rankine Cycle (ORC) systems. Among the different types of volumetric expanders, the screw-type presents a favorable combination of relatively high internal volume ratio (up to 7) and isentropic efficiency (up to 80%) with respect to the optimal pressure ratio at which sub-critical ORCs operate. In particular, single-screw expanders have shown some potential due to their symmetric and balanced configuration that decreases the loads on the bearings. A comprehensive characterization of this type of machine with two working fluids, i.e., SES36 and R245fa, has been carried out in a previous work [1]. Based on the experimental work, friction losses and internal leakages were found detrimental to the expander performance. As the expander requires lubrication during operation, flooded expansion can be beneficial to reduce such losses as well as to improve the expansion process toward a quasi-isothermal behavior. A thermodynamic cycle model has been developed to evaluate the potential improvements on the thermodynamic performance of organic Rankine cycle with flooded expansion and internal regeneration. A semi-empirical model of the expander is included which accounts for the effects of internal volume ratio. The results from the cycle model have used to design an ORC test setup with an independent lubricant oil loop and internal regeneration. The new test rig will be used validate the trends obtained with the cycle model and to further characterize the single-screw expander. The working fluid employed is R1233zd(E) as a replacement for R245fa. [ABSTRACT FROM AUTHOR]

There is significant interest in the deployment of organic Rankine cycle (ORC) technology for waste-heat recovery and power generation in industrial settings. This study considers ORC systems optimized for maximum power generation using a case study of an exhaust flue-gas stream at a temperature of 380 °C as the heat source, covering over 35 working fluids and also considering the option of featuring a recuperator. Systems based on transcritical cycles are found to deliver higher power outputs than subcritical ones, with optimal evaporation pressures that are 4-5 times the critical pressures of refrigerants and light hydrocarbons, and 1-2 times those of siloxanes and heavy hydrocarbons. For maximum power production, a recuperator is necessary for ORC systems with constraints imposed on their evaporation and condensation pressures. This includes, for example, limiting the minimum condensation pressure to atmospheric pressure to prevent sub-atmospheric operation of this component, as is the case when employing heavy hydrocarbon and siloxane working fluids. For scenarios where such operating constraints are relaxed, the optimal cycles do not feature a recuperator, with some systems showing more than three times the generated power than with this component, albeit at higher investment costs. [ABSTRACT FROM AUTHOR]

High efficiency expanders which can cope with fluid-vapour mixtures (i.e wet expansion) at the inlet and during expansion have the potential to increase the power output from thermodynamic power cycles. Volumetric expanders are considered suitable, yet experimental results are scarce and there is no model that can predict the performance of the expansion process. This is mainly due to the knowledge gap on the fundamental aspects off two-phase expansion and the non-equilibrium effects. Therefore, in this work, a variable volume piston expansion chamber is designed. The influence of the main design parameters are investigated by means of a simple deterministic model. Based on initial figures of merit, the component selection and technical layout is presented. The optical access in a later stage will be crucial to allow investigating the mechanistic process of the nucleation and the interfacial effects. This understanding is essential for generalization of the results to other working fluids and geometries. [ABSTRACT FROM AUTHOR]

In recent years, computational fluid dynamics (CFD) has been applied for the design and analysis of positive displacement machines (both compressors and expanders) with numerous challenges due to the dynamics of the compression (or expansion) process and deforming working chambers. The relative motion and in turn, the variation of the gaps during machine operation implies several obstacles for the implementation of reliable CFD models. The majority of the studies reported in literature focused on scroll, twin screw and reciprocating machines. The limitation of the developed methodologies to be applied directly to positive displacement machines with more complex meshing such as that of single-screw has been highlighted in literature. In this paper, a single screw expander is studied by means of (i) a moving mesh technique (dynamic mesh in the Key Frame Remeshing approach) and (ii) a real gas model of a R134a (Peng-Robinson model) implemented in OpenFOAM ®. On the top of that, all the possible techniques that come with the software are investigated in their application to single screw. An useful review of the state of the art CFD with open-source software (OpenFOAM-v1606+ and foam-extend4.0) is therefore carried out. The reliability of CFD model represents indeed the first step on which the design process and further optimization will be based. [ABSTRACT FROM AUTHOR]

From all fossil fuel power production routes, the electricity produced with Gas Turbines (GTs) running on natural gas has the lowest CO 2 emissions. However, if we want to move towards full carbon clean power production, the CO 2 in the exhaust must be captured. The energy impact of a Carbon Capture plant (CC) applied to the micro Gas Turbine (mGT) still remains unclear because few quantitative analyses are available. The low concentration of CO 2 in the GT exhaust gas is disadvantageous from a CC point of view. Exhaust Gas Recirculation (EGR) is one of the technologies used to increase the CO 2 concentration in the GT flue gas. It is potentially an effective method to reduce the high energy-penalty caused by the carbon capture. A typical capture method is an absorber–stripper system where the absorbent is commonly a 30wt% aqueous monoethanolamine (MEA) solution. In this work, a Turbec T100 mGT coupled with a chemical-absorption plant is considered. The entire plant has been simulated using Aspen Plus ® . Simulation results show that the specific reboiler duty is rather constant (around 4.3 MJ/kgCO 2 ) when varying the electrical power output of the mGT. The cycle performance is strongly affected by the thermal energy requirement for the stripping process, decreasing the global electric efficiency around 6.2 absolute percentage points. These results could be a starting point for future energy integrations between the mGT and the CC plant. [ABSTRACT FROM AUTHOR]

Despite appearing as a promising technology for decentralised Combined Heat and Power (CHP), the rather low electrical efficiency of micro Gas Turbines (mGTs) prevents them from being attractive for users with a variable heat demand. Hot water injection in mGTs, achieved by transforming the cycle into a micro Humid Air Turbine (mHAT), allows increasing the electrical efficiency of the units in moments of low heat demand— therefore decoupling heat and electricity production. In spite of previous research regarding simulations, experiments and economic assessments of mHAT technology, the detailed enthalpy and exergy flows between the components remained to be investigated. In the present paper, we introduce and compare the Sankey (enthalpy flow) and Grassmann (exergy flow) diagrams of an mGT based on the Turbec T100 and the corresponding mHAT cycle. Results show that the electrical efficiency of the T100 increases by 2.5% absolute points with water injection, while the total exergy efficiency decreases by only 4.1%. Although there is an enthalpy gain in the saturation tower, exergy actually decreases in this component due to the increase in entropy related to the evaporation of water. The benefits of water injection mostly rely on the increased heat capacity of the air-vapour mixture, the lower fuel consumption, the higher heat recovered in the recuperator, and the reduced power required by the compressor. [ABSTRACT FROM AUTHOR]

Organic Rankine cycle (ORC) systems are increasingly being deployed for waste-heat recovery and conversion in industrial settings. Using a case study of an exhaust flue-gas stream at a temperature of 380 °C as the heat source, an ORC system power output in excess of 10 MW is predicted at exergy efficiencies ranging between 20% and 35%. By comparison with available experimental data, the thermodynamic properties (including those in the supercritical region) of working fluids are shown to be reliably predicted by the SAFT-VR Mie equation of state; this verification is quite important as this is the first time that the SAFT-VR Mie equation of state is used for thermodynamic property prediction of working fluids in their supercritical state in trans-critical ORC systems. Various cycle configurations and the use of working-fluid mixtures are also investigated. ORC systems operating on trans-critical cycles and those incorporating an internal heat exchanger (IHE) are seen to be beneficial from a thermodynamic perspective, they are, however, more expensive than the simple ORC system considered (subcritical cycle with no IHE). Furthermore, ORC systems using pure working fluids are associated with slightly lower costs than those with fluid mixtures. It is concluded that a basic ORC system utilizing pure working fluids shows the lowest specific investment cost (SIC) in the case study considered. [ABSTRACT FROM AUTHOR]

Introduction of water in a micro Gas Turbine (mGT) has proven to be a very efficient way to introduce waste heat in the cycle. The injection of preheated water/steam in the mGT cycle will increase the efficiency of the cycle significantly. Different routes exist for water injection in an mGT cycle. Classical routes, like injection of steam/preheated water or the micro Humid Air Turbine (mHAT) cycle, where water is introduced in the cycle by means of a saturation tower, have shown to have high potential, however do not fully exploit the maximal potential for waste heat recovery. More advanced humidified gas turbine cycles exist on large scale, but these concepts have not yet been applied on mGT scale. In this paper, we study the impact of these different, more advanced, humidified gas turbine cycle concepts on the mGT performance. The different selected cycles – next to the classical Steam Injected Gas Turbine (STIG), injection of (preheated) water and the mHAT – were: mHAT-plus, Advanced Humid Air Turbine (AHAT) and the Regeneration EVAPoration cycle (REVAP ® ). Simulations indicated that humidifying the air of the mGT has a significant beneficial effect on the cycle performance, resulting in increased electrical power output and efficiency. Depending on the different used cycle layout, more waste heat could be recovered from the exhaust gas. The REVAP ® cycle with feedwater preheat was identified as the optimal cycle layout within the selected cycles. Using this concept, the stack temperature could be lowered to 53 °C, corresponding to an increase in electrical power output of 128.7 kW e with a maximal absolute efficiency increase of 6.9% compared to the dry cycle layout (100.1 kW e electrical power output and 35.1% efficiency). [ABSTRACT FROM AUTHOR]

Positive displacement machines (e.g. scroll, twin screw, reciprocating, etc.) are proven to be suitable as expanders for organic Rankine cycle (ORC) applications, especially in the medium to low power range. However, in order to increase their performance, detailed simulation models are required to optimize the design and reduce the internal losses. In recent years, computational fluid dynamics (CFD) has been applied for the design and analysis of positive displacement machines (both compressors and expanders) with numerous challenges due to the dynamics of the expansion (or compression) process and deforming working chambers. The majority of the studies reported in literature focused on scroll, twin screw and reciprocating machines. Furthermore, the limitation of such methodologies to be applied directly to complex multi-rotor machines has been highlighted in literature. In this paper, a single screw expander (SSE) is used as benchmark to evaluate the applicability of different grid generation methodologies (dynamic remeshing and Chimera strategy overlapping grid), in terms of computational resources required, accuracy of the results and limitations. Although, the low-order models have been applied to single screw machines, there is still a lack of CFD analyses due to the particular complexity of the machine geometry and of its working principle. The calculations have been performed with air to reduce the complexity of the problem. to the main results are two folds: (i) the assessment of a numerical strategy with respect to the most critical parameters of a dynamic mesh-based simulation and (ii) the comparison of the pressure field and internal flow features obtained by using different numerical approaches. [ABSTRACT FROM AUTHOR]

The OLV Hemelvaart church in Watervliet dates back from the 16th century and contains valuable panel paintings and wooden artefacts. They need to be preserved in a stable conservation climate. However, due to the old air heating system, the indoor climate is not stable at all. The air heating system creates sudden strong rises in temperature and due to the position of the supply and extraction grilles, the warm air is not evenly distributed throughout the church. Furthermore, the church suffers from moisture problems such as rain penetration and rising damp. In view of improvement measures to the heating system, from March 2012 to March 2014, the temperature and relative humidity was measured on different locations in the church. The ASHRAE conservation classes were used to analyze the data. Both a frequency analysis and an analysis of the short term and seasonal fluctuations of temperature and relative humidity were performed. It was found that the relative humidity of the indoor air was far too high for conservation purposes: during more than 50% of the time a value above 75% was registered in the middle of the church. During a period of two months, the church was permanently heated in order to improve the conservation climate. Compared to the intermittent heating regime, permanent heating caused a more stable climate: the relative humidity level exceeded 75% during 20% of the time, but it remained almost constantly between 60% and 75%. This was attributed to the church walls that acted as a constant moisture source during heating. [ABSTRACT FROM AUTHOR]

The constantly rising energy demand and the depletion of fossil fuel resources currently represent the main concerns for global energy sustainability, alongside environmental issues. Low-grade energy sources have moved into the limelight and Organic Rankine Cycle (ORC) technology is well known for its suitability to recover waste heat. The optimization of the expansion process of an ORC system is crucial in order to maximize the power output, to increase the overall efficiency, and to obtain an economically feasible machine. Scroll, reciprocating, single screw, twin-screw and vane-type expanders are the main technologies. Screw expanders are particularly suited for low-grade heat recovery. The advantages of single screw technology over twin-screw include the balanced loading of the main screw, long working life, high volumetric efficiency, low leakage, low noise, low vibration, and a simplified configuration. In this paper, a detailed geometry-based model of a single screw expander is presented. The model is based on a rotation-dependent function that completely describes the geometry of the screw rotor and the engaging surfaces of the star wheels. A computation of the swept volume at each angular step and of the inlet conditions leads to a solution of the system of differential equations governing the thermodynamics of the expansion process. The model considers heat losses, oil-flooded mixing and leakage paths and permits the investigation of the impact of design modifications on the expander performance. Furthermore, the validation of the proposed model against the available literature is presented. [ABSTRACT FROM AUTHOR]

Increasing energy-demand and environmental concerns are leading to a growing interest in alternative and sustainable energy solutions. Low-grade waste heat recovery through ORC systems is considered to be one of the most feasible eco-friendly energy conversion technologies. In this paper, a comprehensive model of an organic Rankine cycle (ORC) system for micro-CHP applications is presented in order to compare the behavior under part-load conditions of two types of positive displacement expanders, a single-screw expander and a scroll expander. The ORC model is implemented in the AMESim ® environment, which allows system modeling both for steady-state and transient analysis. Typical residential electrical and heating loads are considered to study the performances of a suitable small-scale system. By means of a detailed quasi-1D model for a single-screw expander and a Reverse Engineering (RE)-Computational Fluid Dynamics (CFD) approach for a scroll expander, the performance characteristic maps of both expansion machines, in terms of isentropic efficiency as function of expansion ratio and rotational speed, have been determined and implemented in the AMESim ® model. A comparison between the selected expanders is presented to address the influence of different positive displacement-type expanders on the overall ORC performances at off-design conditions. The capability of the system to meet the requested loads is also discussed. [ABSTRACT FROM AUTHOR]

Micro Gas Turbines (mGT) appear as a promising technology for small-scale (up to 500 kW) Combined Heat and Power (CHP) production. However, their rather low electric efficiency limits their profitability when the heat demand decreases. Hot liquid water injection in mGTs –particularly within the micro Humid Air Turbine (mHAT) cycle– allows increasing electric efficiency by making use of the flue gas residual heat in moments of low heat demand. Based on simulations performed on a Turbec T100 mGT –modified to operate as an mHAT– installed at the VUB, this paper presents an analysis of the economic profitability of such facility running on real network conditions. The study is performed assuming typical electricity and heat demand profiles for a domestic consumer. 25 natural gas and electricity price combinations have been taken into consideration, along with two types of domestic customers –with higher and lower heat demands. Results show that the profitability of the mHAT with respect to the equivalent CHP facility increases with higher electricity and lower natural gas prices. In particular, given a certain number of CHP running hours and a natural gas price, there is a threshold for the electricity price above which the net income of the mHAT unit is always higher than that of the corresponding CHP unit. In addition, water-cleaning costs for the mHAT case appear to constitute only 1 to 2.5% of total running costs. [ABSTRACT FROM AUTHOR]

To improve the performances of the Organic Rankine cycle, several advanced cycle designs are proposed. Because different studies use varying boundary conditions, an assessment of the benefit of the cycle designs is complicated. Furthermore, the inclusion of economic parameters is valuable for a sound comparison. In this work, the subcritical cycle, the trilateral cycle and the transcritical cycle are compared on a thermodynamic and economic basis. The investigated cycles are optimized for three waste heat recovery cases within a temperature range of 100 °C to 300 °C. From a pure thermodynamic analysis only a marginal performance benefit is achieved for high temperature cases with the working fluids under consideration. Therefore, a thermo-economic analysis is provided for the low-temperature case. A multi-objective optimization is at the basis of the thermo-economic analysis and comparison. The thermodynamic performance of the cycles is compared with equal boundary conditions and actual cases are used. The results of such investigation are particularly interesting for manufacturers of ORCs. [ABSTRACT FROM AUTHOR]

Micro Gas Turbines (mGTs) were considered very promising for small-scale Combined Heat and Power (CHP) production. They however never fully penetrated the CHP market, resulting in a limited market share. Due to their low electric efficiency (30% versus 80% CHP efficiency), the operation of the mGT is strongly heat-driven. In applications with a non-continuous yearly heat demand, like domestic heating systems, the mGT would be shut down for long periods, resulting in a reduced amount of yearly running hours. These limited running hours make the mGT as small-scale CHP less profitable compared to other technologies, like reciprocating engines. Converting the mGT into a micro Humid Air Turbine (mHAT) offers a solution. The waste heat in the exhausted gases is recovered in the mHAT by evaporating auto-raised hot water behind the mGT compressor, resulting in a higher electric efficiency and a more flexible mGT operation. In this paper, we present the results of experiments on a modified Turbec T100 mGT. As a proof of concept, the mGT has been equipped with a spray saturation tower to humidify the compressed air. The goal of these experiments was to evaluate the beneficial effect of compressed air humidification on the mGT performance. Two stable runs at constant pressure ratio and rotation speed were recorded during water injection. Final electric efficiency results show a relative electric efficiency increase of 1.2% and 2.4%. These changes are however in the range of the accuracy of the measurements. Further experiments are therefore necessary to fully characterise the behaviour of the mHAT at part and nominal load. Fine-tuning of the water injection control strategy is also identified as a key parameter to reduce the auxiliary power losses. [ABSTRACT FROM AUTHOR]

Abstract: Understanding the heat transfer mechanism from the combustion gases to the walls inside an internal combustion engine is key in the search for higher efficiencies, higher power outputs and lower emissions. Current heat transfer modeling concepts have been reported to be inaccurate for hydrogen engines. To investigate the heat transfer mechanisms in a hydrogen engine, we have measured the instantaneous heat loss inside a spark-ignition engine at three locations. To determine the effect of the throttle position, compression ratio, ignition timing and air-to-fuel ratio in the entire parameter space systematically, techniques of Design of Experiments are applied. The experiment has been repeated for methane, gasoline and methanol to compare hydrogen with other fuels and to build a database for the development of a fuel independent heat transfer model. The paper shows that the effect of the engine factors is similar for all the fuels. However, the heat loss to the cylinder walls of hydrogen is only at the same level of that of the other fuels for very lean mixtures. The engine efficiency drastically reduces for rich mixtures as a consequence, indicating that a lean mixture in combination with boosting and external gas recirculation should be used to obtain high power outputs with high efficiencies for port fuel injected engines. [Copyright &y& Elsevier]