A COMPUTER PACKAGE FOR DAIRY PLANT REFRIGERATION SYSTEMS Q. Tuan Pham University of New South Wales

Summary F Software has been developed at UNSW under a DRDC-funded project to simulate refrigeration systems F We report test results and potential uses in design, operation and optimisation

Rationale F 30 to 50% of electricity in dairy industry is used in refrigeration F Staff are more concerned with production than with energy efficiency F Most industrial refrigeration systems can improve their energy efficiency by about 10 to 15% with negligible capital spending. F Software helps identify possible savings and inefficiencies

A simple refrigeration system Generating cold Using cold

A dairy plant refrigeration system Generating cold Using cold

Energy saving 1: Generation of cold F Proper selection of compressors, condensers F Better operation of engineroom (compressor schedule) F Maintenance of equipment, e.g. –prevent condenser fouling –remove noncondensables (air) F Improved control in engineroom, applications F Energy recovery

Energy saving 2: Use of cold F Improved chilling and freezing methods F Better chiller and freezer designs F Shifting loads to reduce peak loads F Eliminating wastages, e.g. –door infiltration –excessive fan heat –poor insulation

Example: Effect of compressor loading on energy efficiency

Example: non-optimal cooling regime OVER-DESIGN: Capital cost $$$ UNDER-DESIGN: Operational problem Cooling/freezing time Product heat load SLOW COOLING Quality/safety problems Compliance problems FAST COOLING: High energy cost Quality problems Optimum

Example: Poor airflow distribution in a chiller

Example: Air infiltration through doors

Simulation software F General purpose simulation software: Aspen Plus, Hysim... F General purpose refrigeration software: RADS F Industry-specific refrigeration software: DRDC-UNSW suite

What software can do F Predicting changes to refrigeration requirements with –changes in processing operations –changes in product type or throughput F Comparing predicted with actual power consumption - identify wastage F Suggesting alternative schedules for freezers and chillers to reduce peak power charges

Organisation of programs Application heat load Plant heat load Power consumption Graphs, reports User inputs Outputs:

Validation Tests: Objectives F Check that all applications can be modelled F Check that accuracy is acceptable F Check ease of use and robustness

Refrigeration system at a Sydney dairy plant

Heat transfer results for a milk pasteuriser

Heat transfer for cream pasteuriser

Total compressor power consumption

Using the Software in Optimisation F Design of new refrigeration plants F Upgrading of plants –replacement of old equipment –new products –changed flowrates –new processes –changes in schedules

Using the Software in Optimisation (cont) F Checking performance to pinpoint defects F Optimising design and operation –Reschedule applications to shift peak load? –Turn off fans and refrigerators temporarily? –One big compressor or several small ones? –One or two stage compression?

Acknowledgments Dairy Research & Development Corporation Dairy Process Engineering Center Dairy Farmers

How about a Software Demonstration?

To describe an Application... Clicking on 1 starts APDATA.EXE Clicking on "Create a Chiller" brings up... Clicking on ”Page 8" brings up... Clicking on ”Help" brings up...

To describe a Plant... Clicking on 3 starts PLANT.EXE Clicking on “Applications” starts the Applications list Double-clicking on a textbox brings up the Application window Enter name of file created by APPLIC.EXE here

To describe an Engineroom... Clicking on 5 starts ENGROOM.EXE Clicking on p.1 brings up the General Layout window Clicking “Details on level 1” brings up...

To describe an Engineroom (cont)... Clicking on 5 starts ENGROOM.EXE Clicking on “Compressor models” brings up the Compressors window Clicking on a textbox to enter models details...

To describe an Engineroom (cont)... Clicking on 5 starts ENGROOM.EXE Click on Operating conditions... Click on a textbox...

To carry out routine refrigeration calculations... Clicking on 7 starts Basic Refrigeration Calculations Clicking on 8 starts basic compression cycle Clicking here gives results

That’s it folks! This presentation can be downloaded from (go to bottom of page)