Barcelona 7th – 9th July, 2014

Development and Implementation of

Educational Portable Equipment for Artificial Cold

Production Subjects

Daniel Sánchez García-VacasRamón Cabello LópezEnrique Torrella AlcarazJorge Patíño PérezRodrigo Llopis DoménechCarlos Sanz Kock

David Conesa SorollaHugo Negre Gómez

Carlos Rodríguez RodrigoJosep San Mateo Sanahuja

INDEX

Introduction1

Experimental facility2

Results3

Intr

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1Educational Context

• The European educational framework based on ECTS credits system pretends;

A teaching process focused mainly on student learning. A quantification of student workload: class attendance, seminars,

practice sessions… Development of students’ skills, abilities and competencies.

• How to achieve students’ skills and abilities? using practice sessions, because…

Students can be in touch with “intangible” concepts showed in class: radiation.

Consolidating new theoretical concepts. Developing of new skills and abilities. Students change its theoretical mind into a practical one. Sometimes it introduces a completely “new World”.

Intr

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1Thermal Machines and Engine Area

• Our particular case:• Department of Mechanical Engineering and Construction. Jaume I

University• Mechanical degree, Master degree.• Subjects related with heat transfer:

Thermal Engineering. Design of heat exchangers. Thermoelectric Power Plants. Air Conditioning. Combustion Infrared Thermography Cogeneration. Refrigerating technology …. etc.

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1Practice Sessions

• All subjects have several practice sessions given in the same laboratory. • Some examples: Heat transfer through plane surfaces and extended

surfacesEnergetic demand in buildings (LIDER) and radiation heat transferAir conditioning and CombustionCogenerationRefrigerating plants based on vapour compression technology

Intr

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1

• Regarding to artificial cold production subjects:

In some cases research plants or facilities are used to teach students.

It has some advantages and disadvantages: Advantages

- Main variables (temperature, pressure, mass flow…) are measured.

- Very close (or similar) to the real one.- Since the refrigerating facility has been studied previously, is

totally known. Disadvantages

- High electrical energy consumption.- Secondary loops are necessary heat transfer rejection

and/or heating.- They are very expensive and heavy.- They can be modified continuously.- Can be difficult to understand for students.

Practice Sessions

Intr

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1Main Objectives

• OBJECTIVS:

Development a portable and lightweight educational equipment based on vapour compression simple… in order to be used in theoretical classes and practice sessions.

• REQUIREMENTS:

Inexpensive. Powered by 240 VAC and 50 Hz Portable and lightweight. Vapour compression cycle without internal heat exchanger (IHX). Easy to use. Transparent heat exchangers condensation and evaporation

processes must be visible. All the main variables (temperature, pressure…etc.) must be

registered.

INDEX

Introduction1

Experimental facility2

Results3

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Structure

• Portable and lightweight • The structure has been assembled with 25 x 25 x 1.5 mm square steel

profile.• Moreover, pine wood panels has been bolted to square steel profile to

reduce weight. Dimensions

Hight: 645 mmWide: 670 mmThin: 250 mm

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Refrigerating Diagram

• Vapour compression cycle:

[1] Hermetic compressor [2] Oil separator [3] Transparent condensator [4] Sight glasses [5] Liquid receiver [6] Filter-drier [7] Micrometric valve [8] Transparent evaporator [9] Pressure transducers [10] High and low pressure gauge

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Main Components

• Transparent heat exchangers glass and ground glass • Maximum operating pressure 12 bar with Nitrogen

• Accordingly we choose a low pressure refrigerant R600a (isobutene)• Hermetic compressor form EMBRACO Model: EMT30CDP, with a cooling

capacity of [130 ÷ 409 W] working at [-5 ÷ 15 ºC] (evaporating) [35 ÷ 65 ºC] (condensing).

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• Two DC fans are installed in order to modify easily the condensing and evaporating temperature. Both have a voltage regulator to modify its flow.

Main Components

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Data Acquisition System

• The DAQ system have to be inexpensive and flexible to be modified in the future.

• Accordingly we use the open hardware platform ARDUINO. Model MEGA 2560 with 54 digital i/o, 16 analog inputs, 256 kB internal memory and a clock speed of 16 MHz.

• Supply voltage of 7 – 12 VDC via USB or with a power supply, depends on the number of transducers.

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• Transducers:

Number Measured variable Measured range Supply voltage Accuracy Output signal

5 Temperature (ºC) -10 ÷ 85 ºC 5 VDC ± 0.5 ºC Digital

4 Temperature (ºC)Relative humidity (%)

0 ÷ 100 %-40 ÷ 125 ºC

5 VDC± 2 % HR± 0.2 ºC

Digital

2 Pressure (bar)0 – 8 bar

0 – 15 bar24 VDC

± 0.25 % full of range

Analogical (4 – 20 mA)

1 Electric Power (W) 0 – 625 W 24 VDC± 0.5 % full of

rangeAnalogical

(0 – 5 VDC)

Temperature: 18DB20

Tª / HR: DTH22 Pressure: J&C p499

Data Acquisition System

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• Two LCD have been used to show temperature, pressure, power consumption and temperature and relative humidity of air.

• The DAQ has two power supplies with 5 VDC, 24 VDC y 8 VDC to supply Arduino, transducers and evaporator and condesator fans.

Data Acquisition System

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Assembly Costs

• The assembly costs included the price of all elements used.• The total amount includes IVA and the corresponding discount (~40%).• 4 sections have been defined:

Structure: 30.58 € Refrigerating cycle: 291,38 € DAQ + Transducers: 287,06 € Electrical installation: 90,59 €

Total: 699,61 €

Total weight:

18,73 kg

30.58

291.38

287.06

90.59

StructureRefrigerating cycleDAQ + transducersElectrical installation

INDEX

Introduction1

Experimental facility2

Results3

Resu

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3Results

• A compact and portable educational equipment based on vapour compression cycle, has been developed and implemented with a DAQ system.

• In order to show students all the equipment possibilities, an easy manual has been developed:

Identification of main components. Representation of the cycle in the log P-h diagram. Representation of the air evolution in the psychometrical diagram. Calculation of the power exchanged by evaporator and condenser Calculation of the refrigeration facility COP. Calculation of the refrigerant mass flow rate. Study how affects variations of variables in the energetic behavior of the

cycle.• Since this project has been developed in the present academic year 2013/2014, the reactions of the students and teachers working with this unit have not been registered.

Thank you!!

Development and Implementation of

Educational Portable Equipment for Artificial Cold

Production Subjects

Barcelona 7th – 9th July, 2014

Questions? Please do not hesitate to contact me if you require further information: sanchezd@uji.es