Components RA2

Through multidisciplinary research and collaboration, Components will develop cost efficient solutions for compact component heating, cooling and surplus heat. This will be based on the use of environmentally friendly, natural working fluids. E.g. ultra-efficient heat exchangers, compressors, components for cost-effective implementation of heat pumping and rotating machinery suited for natural working fluids will be developed.

Potential innovations:

  • Compressor concepts for targeted fluids, capacity ranges and operational conditions, e.g. semi-hermetic compressors able to operate at high suction temperatures and pressures
  • Expander concepts for targeted fluids, capacity ranges and operational conditions
  • Heat exchanger designs for power and heat pumping cycles
  • Components for cycle enhancement, e.g. ejector concepts for off-design operation

Components consists of the following Work Packages (WP)

RA2  Components Armin Hafner   NTNU
WP2.1 Heat exchangers Geir Skaugen SINTEF Energy Research
WP2.2 Work recovery & compressors Christian Schlemminger  SINTEF Energy Research
WP2.3 Natural working fluids Trygve M. Eikevik NTNU

2018 results

Heat Exchangers

The work related to heat exchanger (HX) for cold thermal energy storage (CTES), applicable for display cabinets in supermarkets continues, with focus on increased performance of display cabinets and power peak shaving. Experience has been gained on how the derivative free optimisation framework NOMAD can be implemented for process and HX optimisation. For simple Rankine cycles the gradient based method was compared to NOMAD in terms of time consumption and robustness.

The work on 3D-printing continues to streamline the process from HX geometry optimisation, on-screen visualization, 3D-editing and finally 3D-printing. The main outcome was a visualization scripting with Python toward Paraview, a well-known visualization toolkit for CFD.

HighEFF Lab – Heat Exchanger Laboratory was designed. The two test rigs cover: HX prototype test rig up to 40 kWth and a small-scale heat transfer coefficient and pressure drop test rig.

Work recovery & Compressors

Design and testing of Multi-ejector expansion modules continue. These devices are substituting standard high-pressure electronic expansion valves in refrigeration systems.

Two expansion devices designed for R744 (CO2) refrigeration systems (capillary tube and fixed geometry ejector) were experimentally tested to determine performance in different ambient conditions. Tests and numerical investigations concluded that ambient conditions did not significantly affect the operation of the capillary tube and the R744 ejector.

Three approaches to perform modelling of piston compressor processes have been developed: 1D model; 3D CFD model; and 3D FEM impact model. These modelling approached give complementary insights into the piston compressor processes and how to optimize compressors for increased efficiency and reliability. A measurement campaign has been performed with the prototype compressor for butane. The prototype compressor shows high isentropic efficiencies in the order to 0.70 to 0.78, nearly constant over pressure ratio investigated. The volumetric efficiency declined from 0.89 to 0.75 with increasing pressure ratios.

Natural Working fluids

The investigations on hydrocarbon heat transfer and pressured drop in small pipes continues. Calibration was done against correlation for single phase flow in vapor form; a 5.6 % deviation for the pressure drop; 1.6 % for heat transfer coefficient. For fluid visualization, a highspeed camera will be installed in 2019.

A library for general humid gas "hglib" was built based on "hxlib" library. hglib is connected to THERMOPACK, enabling to calculate humid gas as real gas. The EOS, e.g. PR, EOCGC, GERG2008 have been tested with the reference result by hxlib at low pressure, and EOCGC, GERG2008 perform well. Available methods for calculating the viscosity of a hydrocarbon mixture at high pressures and temperatures were investigated. A sufficiently general correlation is difficult. The TRAPP method is quite accurate but tends to overpredict the viscosity. The CS2 model has a similar accuracy, but underpredicts the results. For both models the density calculations needs to be as accurate as possible. Refprop results are generally better than TRAPP and CS2 with some exception

2017 Results

Heat Exchangers:

Heat exchanger for cold thermal energy storage (CTES), applicable for display cabinets in supermarkets, has been developed and implemented into a dedicated CO2 laboratory refrigeration cycle. The CTES will increase the performance of display cabinets and enable power peak shaving.

A new laboratory rig, financed by the infrastructure project HighEFFlab, for testing of heat exchangers used in low temperature heat to power applications is under planning. A pinch point analysis of relevant hydrocarbon working fluids with low ODP and GWP has been performed to investigate which working fluids are the most interesting for testing in the laboratory rig and the optimal operating conditions for these.

Work recovery & Compressors:

Design and testing of Multi-ejector expansion modules, intended as a substitute for standard high-pressure electronic expansion valves, for performance mapping of four ejector cartridges is completed. Results shows that four ejector geometries perform their vapour compression duties efficiently within the assumed range of operating conditions, offering the highest ever recorded values of ejector efficiency up to 36.8%. the liquid compression reduces the effectiveness significantly, where the highest recorded recovery values of ejector efficiency were equal to 12.6%.

The propane - butane High Temperature Heat Pump test facility has been installed successfully and delivering heat sink outlet temperature of 116 °C. The R600 compressor from DORIN is functioning within expectation with a total compressor efficiency of 71%.

Natural Working fluids:

In the evaporator/sublimator process of CO2 (R744) ultra-low temperature cascade heat pump system, it is known, as a problem, that dry-ice blockage makes the system operation fail. The design of an expanding channel for the evaporation/sublimation process is one solution to solve the problem. In order to give better understanding to heat transfer process in the refrigeration system, particular attention is focused for CO2 dry-ice solid-gas two-phase flow to obtain the effectivity of heat transfer and to verify the flow-phenomena where a visualization test apparatus is placed horizontally. Development of a mathematical model for baseline and the enhanced systems for the next generation of refrigeration systems for chilling of fish in fishing vessel. By applying adapted ejector technology and parallel compression, these units can be applied globally with a significant energy saving compared to traditional system layouts.

Armin Hafner

Professor
Name
Armin Hafner
Title
Professor
Organization
NTNU