Project planning, material and equipment
During test equipment and installation, the latest versions of applicable documentation and international standards specific to such systems must be taken into account.
This technical specification is intended to define the technical parameters of construction and installation to be observed in systems for the preservation and freezing of fresh food, medicine and other products, designed to meet the specific storage conditions for each case. For the correct selection of the equipment to be provided and installed, a design as detailed as possible should be prepared by a skilled technician and at least the following data should be specified:
a) Using an appropriate calculation method and the most reliable method possible, estimate the required Cold Load, taking into account: · Weather conditions of the location where the project will be implemented; · Required room dimensions: walls, floors, ceilings and doors; · Building elements: dimensions and materials of walls, floors, ceilings, thermal insulation and others; · Heat dissipation sources: people, lighting equipment, various electrical/electronic equipment and others; · Air infiltration through door openings; · Other criteria that may affect this heat load.
b) Selection of cooling equipment to be supplied and installed based on the previously evaluated thermal load and customer needs and expectations.
c) Brand selection of refrigeration equipment to be supplied and installed, taking into account the most reputable brands such as DANFOSS, EMBRACO, ELGIN, RECAM, TECHUMSEH and others.
2 GENERAL CHARACTERISTICS The characteristics described below are designed to introduce the basic conditions for a flawless equipment supply. Inspection, evaluation, adaptation to specific and complementary equipment and
COLD/FREEZER ROOMS TECHNICAL SPECIFICATIONS
must ensure compliance with standards, the safety and operational efficiency requirements of the installation and detailed calculations.
2.1 System of Units: All quantities shall be stated in units of measurement of the Metric System. However, exceptions may be made for products generally manufactured to other standards, such as copper pipe, insulating sleeves, screws, nuts and others; these are usually specified in British Standards. In the event of a conflict between the Metric System and another system, the former shall prevail.
2.2 Drawings, Documentation and Other: All drawings and catalogs, if any, shall indicate the materials used, dimensions, types of finishes, fixtures and other information deemed necessary to better understand and demonstrate compliance with the requirements of these specifications.
2.3 Instruction Manual: The instruction manual of the recommended refrigeration units should contain at least the following information: • General Index; • Procedures for the different operating modes of the equipment; • Complete Manual of each device manufacturer, including installation details, operation and maintenance, and a quick rotation parts list for subsequent reinstallation; • Preventive and corrective maintenance instructions; • If possible, it should also include a list of agents and/or local representatives of the recommended brands.
2.4 Warranty: The supplier shall ensure that the equipment, whether manufactured by the supplier or supplied in whole or in part by other suppliers, complies with the requirements of these specifications and is free from defects in production, raw materials or workmanship. The relevant warranty period and scope of application shall also be specified.
3.1 Insulated Panels: The main function of cold/freezer storage room insulated panels is to maintain and control the internal room temperature. Today, refrigeration contractors use isothermal panels for cold, freezer rooms, freezing tunnels, warehouse partitions and other commercial and industrial areas. Due to their easy installation application and portability with a practical connection system and fittings, isothermal panels for cold/freezer rooms have become the choice of major constructors for covers for industrial and commercial buildings. They can be installed in almost any environment and provide efficient thermal insulation, and today the internal temperature of the environments has become a major competitor for some users or processes. The portability of insulated panels for freezer allows the internal environment to be expanded or reduced as needed, which is one of its great points, thus providing an ideal investment without wasting space or materials. Insulated panels for cold/freezer rooms can be manufactured in thicknesses of up to 200 mm and in the widest possible lengths and widths to meet the requirements of each customer and especially each project. It enables and thus reduces the number of connections between them for better thermal insulation, regardless of the dimensions of the room. Various methods are used to join isothermal panels together, the most common and effective being the male-female (or double male-female) system and the embedded hook system, which gives the joint a very good airtightness and rigidity required for a solid assembly. The internal hook fixing system means greater speed and ease of assembly and disassembly compared to other systems used, as a 3/4 turn of the wrench is sufficient to achieve a perfect fit between the panels. 3.1.1 Structure: Insulated panels consist of: Coating – The outer and inner coating of insulated panels can be made of various sheet materials, usually 0.5 mm thick: Lacquered steel, galvanized steel, natural or lacquered
aluminium, stainless steel, rigid plastic and other materials. The base colour is white, but can be supplied in the colour of the Designer or Owner’s choice. Insulation – Insulated panels used in cold/freezer storage rooms are manufactured with rigid polyurethane foam insulation with an average density of 40 kg/m³, giving them a thermal conductivity coefficient (U) as specified in the table below. Connection system – As specified elsewhere in this document, the connection system between the insulated panels shall be a recessed hook setting; in this case, the panels are connected by turning a square key on a metal shaft.
3.1.2 Dimensions: Length – As specified elsewhere in this documentcold roominsulated panels can have a maximum length of 12 meters as required by each project due to production constraints. Width – The width of insulated panels for cold rooms is normally 1,180 mm; Thickness – The thickness of insulated panels for cold/freezer rooms can be 60, 75, 120, 150, 180 and 200 mm, depending on the required temperature inside the room. Thickness U (mm) (kcal/h.m2 . o C) 50 0.042
3.1.3 Accessories: For a good installation of insulated panels for cold rooms, manufacturers offer a range of mounting accessories, consisting of internal and external angles of equal or unequal nails, U-shaped profiles, rods, rivets and others, made of material and coating color. In addition,in cold storageThere are also silicone-based sealants suitable for use in negative temperature environments.
3.2 Cold/Freezer Room Door The cold/freezer room door is the element responsible for opening access to the inside; on the one hand, it must allow access to the inside of the room and at the same time provide a similar or higher thermal insulation quality than the insulated panels of the room. The door is a special type of insulated panel and is likewise composed of: · Internal and external cladding in sheet metal of lacquered steel, stainless steel, galvanized steel, aluminum or other suitable material; · Rigid polyurethane foam insulation with an average density of 40-43 kg/m³; · Internal substructure made of anodized aluminum profile. The cold/freezer room door, on the other hand, must have suitable air-tightness properties and therefore have a perimeter seal and is usually made of double alveolus rubber on a PVC support. It can be of different types to meet the needs of each specific project: a. Hinged doors with openings up to 1,200 x 2,200 mm, produced in small thicknesses on the outside and the remaining thicknesses on the inside, where good appearance and high performance are required; the value of these partial thicknesses depends on the temperature inside the relevant room: i. refrigeration (0 ° C) – external thickness 40 mm, internal thickness 20 mm; ii. freezing (-20 ° C) – external thickness 40 mm, internal thickness 60 mm; iii. superfreezing (-40 ° C) – external thickness 40 mm, internal thickness 100 mm. b. pivot overlapped doors – larger than those used in the previous type of door and for openings up to 1,500 x 2,500 mm, the locking device is overlapped in the panel. The total thickness, in this case, is:
. Cooling (0° C) – 75 mm thick; ii. Freezing (-20° C) – 100 mm thick; iii. Superfreezing (-40° C) – 140 mm thick. c. Sliding doors - This type of door is designed for applications where space is limited. The sliding rails for this type of door are made of structural carbon steel or stainless steel with an anti-corrosion treatment. The locking devices are injection-molded and painted with epoxy paint and the adjustable hinges are made of stainless steel and composite. The refrigerating door to be used in each case must always be well specified, in particular in accordance with the following characteristics: Dimensions; Room service: cooling, freezing or superfreezing; Covering material; Insulated panel or wall mounting; With or without shoulder; With or without threshold; Opening to the left or right; Covering material for internal and external surfaces.
3.3 Equipment and Accessories
3.3.1 Cooling Unit Monoblock cooling unittype will integrate the compact condenser, evaporator, compressor and control system of the unit as a whole in a housing with only one mounting base plate. This type of units can be used in various fields of activity – hotels, restaurants, agriculture, chemical industry, medicine and conservation and other areas where cold storage is required at various temperature levels from 5 to -20o C. Compact refrigeration units consist of base, condenser coil, compressor, condensing fan motor, evaporator coil, evaporation fan motor, refrigeration circuit evaporator and a complete set of control, adjustment and control devices.
As mentioned above, there is a wide range of cooling units for specific applications, from the smallest and simplest to the most complex. The cooling unit must be sized for each case, taking into account the specifics of each project. The installation of this type of cooling unit is very simple, safe and does not require great technical expertise, and is carried out using the appropriate brackets supplied with the unit and expanding metal anchor bolts of the appropriate diameter, taking into account the weight of the unit, and following the manufacturer's instructions. Base The base of the condensing unit must consist of a metal frame made of galvanized sheet steel of appropriate dimensions, with good rigidity, protected against corrosion, electrostatically painted over enamel paint on anticorrosive primer. In the case of a closed unit, the panels must be removable to allow easy access to the inside of the machine. The panels must be suitably treated so that they are resistant to the effects of time and the external environment throughout their life. In monobloc and compact units, the base must be able to accommodate all the cooling system components, including all control accessories. The base shall be covered with a cabinet, which is a monoblock structure made of aluminum with a smooth and shiny surface to facilitate cleaning, but may also be white epoxy paint or stainless steel cladding. Condenser Coil The condenser unit coil, i.e. refrigerator condenser, shall be constructed of seamless copper tubes of appropriate diameter and coated aluminum fins attached to them by mechanical expansion, preventing direct contact with the copper tubes. The coil shall be leak tested at 350 psi at the manufacturer's facility.
The condenser is the component of the refrigeration cycle responsible for transferring heat to the outside air or water or a combination of the two, known as an evaporative condenser. The gas, which has high pressure and temperature values, cools and liquefies as it passes through the condenser coil, transferring the sensible and latent heat of condensation.
Compressor The compressor is one of the main elements in the refrigeration system; It is its heart. Its function is to increase the pressure of the refrigerant and promote its circulation throughout the system. The main types of compressors are: alternating, rotary, vane, screw and scroll. And, in terms of structure, compressors can be classified as hermetic, semi-hermetic and open. In hermetic compressors, the compressor itself and the electrical are located in the same casing, and the input and output access is shown only to the electrical connections of the electric motor.
This type of compressor works only with halogenated refrigerants and the refrigerant vapor comes into contact with the motor winding, cooling it. These compressors are commonly used in domestic refrigeration and air conditioning units with power up to 30 kW (8.5 TR). Semi-hermetic compressors are similar to the previous types, but allow the head of the housing to be removed, providing full access to the valves and pistons. In open compressors, the compressor drive shaft passes through the housing, allowing it to be driven by an external electric motor.
These are mainly large compressors operating on ammonia. The choice of the type of compressor to be used depends mainly on the power of the installation. The refrigeration unit can be equipped with one, two or three compressors, depending on the cooling power required. Generally, the compressors used in refrigeration units for small-sized cold/freezer rooms are of the hermetic rotary, piston or screw type, mounted on vibration isolators, depending on the production, cooling power and other technical and commercial factors.
As mentioned above, the compressors are driven by electric motors that are internally protected against overloads and are suitable for voltage variations of up to 10% of the nominal value. These motors are cooled by the suction refrigerant flow and can be equipped with crankcase heaters. For additional protection of electrical components, devices preventing phase reversal (in three-phase units) or others should be installed in the distribution boards, depending on the requirements of each project.
Condensing Moto-Fan Condensing moto-fan units are generally axial with the paddles pushed forward, made of stamped plastic, aluminium or galvanised sheet steel, statically and dynamically balanced, directly connected to the motor-driven axle.
The evaporator motor fan should be low noise. Depending on the cooling capacity of the evaporator unit, the driving electric motor can be single-phase or three-phase. Evaporator Coil The evaporator coil should be made of seamless copper tubes of sufficient diameter and coated aluminum fins that prevent direct contact with the copper tubes and should be attached to them by mechanical expansion. The coil should be tested for leakage at 350 psi. The fins increase the overall area of heat exchange and thus increase the heat transfer efficiency.
Due to this largest area, these evaporators can be more compact than straight pipe without compromising the heat absorption capacity. They can have their own gas collectors/distributors at the inlet and outlet for optimisation of refrigerant gas distribution. At the bottom, there should be condensate collector trays to collect water from the defrosting process, made of the same material as the unit cabinet. The inner tray prevents air leaks and concentrated water flow from the defrosting process to the drain, preventing unwanted ice formation in the tray and heating of the cold/freezer room during defrosting. It eliminates the disadvantages of water condensation outside during the defrosting phase. The outer tray with rounded corners, tiltable and removable for better access to the defrosting system and cleaning. Evaporator Moto-Fan Evaporator moto-fan units are generally axial, with paddles pushed forward, made of stamped plastic, aluminium or galvanised sheet steel, statically and dynamically balanced, directly connected to the motor-driven axle. The evaporator moto-fan should be low noise. Depending on the cooling capacity of the evaporator unit, the drive electric motor can be single-phase or three-phase, Cooling Circuit The pipe to be applied in the execution of the cooling circuit for this type of cooling equipment should be malleable copper up to ¾” diameter and solid type for larger diameters.
In the first case, the bends should be made with the help of suitable tools - pipe bending tools or springs - and changes on each length should be avoided at all costs. In case of rigid pipe joints, they should be used and the joint should be properly welded and carefully examined. Refrigerant lines should be designed and implemented to fulfill the following functions: - To ensure proper liquid supply to the pipe Evaporator; -
Allowing the flow of refrigerant gas without excessive load losses; - Preventing oil accumulation in low areas; - Preventing oil leaving the compressor from being retained in the piping system; - Preventing liquid from entering the compressor, both when running and when stopped; -
To keep the circuits clean and free of moisture. As for the design, the refrigerant lines: - Must be arranged in such a way that they do not affect the operation of other components or prevent access to other organs or control devices; - Must be protected against shocks, especially in the case of small diameter and insulated pipes; For the design of the refrigerant pipes, it is necessary to know: -
Oil circulation must be ensured; - Condensation must not form in the pipes and the liquid flow formed in the condenser must not reverse its direction; - Abnormal noises or vibrations must not occur in the pipes; - The dimensions of the pipes must keep the load losses to a minimum. In the refrigeration circuit, in addition to the larger components - condenser, compressor and evaporator coils - the filter drier, sight glass and thermodynamic expansion valve, service valves and all operating control devices - low and high pressure switches - must still be included. Filter Drier Filter driers are components installed in the refrigeration system and have the function of retaining residual moisture, acids and solid particles. They are manufactured from copper or steel tube bodies.
COLD/FREEZER Cold storage TECHNICAL SPECIFICATIONS
Their interior has a coarse screen at the inlet and a fine screen at the outlet, and a moisture absorbing desiccant is placed between the screens. The filter should be installed in a vertical position with the outlet facing downwards (when installing the liquid line desiccant in a vertical position, it is necessary to ensure that the inlet is at the top and the outlet is facing downwards. In this way, always the refrigerant Filter, so that the drying capacity is used to the best possible extent). When this position is not possible, they can be installed horizontally, but never vertically upwards.
With the advent of several alternative refrigerants, several desiccant filter options have been developed to respond to the characteristics of each refrigerant. The desiccant filter consists of desiccant particles and should be selected for the specific application, considering the type of refrigerant, operating pressures and mass flow. Sight Glass A very important component in refrigeration systems, especially in medium to large machines, it plays an important role in indicating the flow of liquid through the high pressure liquid line and in some cases, moisture in the system. The sight glass is used to indicate the absence of liquid in the thermostatic expansion valve.
The presence of steam bubbles on the display indicates, for example, a lack of load, low subcooling or partial desiccant filter blockage. Typically, the display is equipped with a colour indicator that changes from green to yellow when the moisture content of the refrigerant exceeds a certain value, in which case actions must be taken to replace the desiccant filter. The colour display is reversible, i.e. when the installation is dehumidified, for example by replacing the line desiccant filter, the colour changes from yellow to green again. Thermostatic Expansion Valve Thermostatic expansion valves regulate the injection of refrigerant gas (in liquid form) in evaporation units and thus the amount of steam drawn in by the compressor. The injection is controlled by the superheating of the refrigerant. The various thermostatic expansion valve sizes and types cover different valves designed for specific applications. The valves are supplied with threaded, welded or bimetal connections in copper/stainless steel.
In addition, the expansion device allows the pressure of the liquid leaving the condenser and entering the evaporator to be reduced, and yet, a sensor bulb keeps the superheat at the evaporator outlet constant. This is achieved by releasing more or less refrigerant into the evaporator. Expansion valves can be externally balanced (the pressure at the top of the diaphragm is the evaporator outlet) and internally balanced, i.e. the pressure below the diaphragm is the evaporator inlet pressure. Refrigerant O R404A is an azeotropic mixture of hydrofluorocarbonates - HFC -, consisting of: R125 - Pentafluoroethane (CF3CHF2), 44%, R134a - Tetrafluoroethane (CF3CH2F), 4%, R143a - Trifluoroethane (CF3CH3), 52%. It has the following properties: R404A has a temperature change of less than one degree during isobar processes. All components are from the HFC group. The three components of the mixture are the cause of low pressure in isentropic compression processes. · R143a is flammable; however, the presence of a high proportion of R125 makes the mixture non-flammable even if a leak occurs. · Compressors must use Ester-type synthetic oils to be miscible with the boiling refrigerant vapor inside the evaporator. · If a leak occurs that is more than 10% of the total amount of the system, it is mandatory to change the entire refrigeration system liquid. In the case of an azeotropic mixture, when a leak occurs, the refrigerant with the greater partial pressure will exit the refrigeration circuit first. The remaining product in the system is no longer R404A and it is not possible to restore the original proportions of the components. · Critical point: - Temperature = 72 ºC - Pressure = 37.2 bar
- Density = 0.484 kg/dm3 Liquid phase at 25 ºC: - Density = 1.04 kg/dm3 - Specific heat = 1.64 kJ/kg ºC Gas phase at 1.013 bar: - Boiling temperature = - 46 ºC - Boiling point = - 46.4 ºC - Specific heat = 0.88kJ/kg ºC Saturated vapor: - Density = 5.41kg/m3 ODP = 0 GWP = 0.0555 In general, to be a good refrigerant, a substance must have the following properties: • Can liquefy (condense) under moderate pressure; • Can vaporize at pressures above atmospheric pressure; • Can have a low specific volume (small volume in relation to its weight); • Should have a high latent heat of vaporization; • It should be chemically stable (not changeable even with repeated changes of state in the cycle); • It should be non-corrosive; • It should be non-flammable; • It should be non-toxic; • It should allow the leak to be easily detected; • It should not hit the lubricating oil or cause an undesirable effect on other components of the refrigeration cycle; • It should not hit or rot the food if the leak occurs.
Thermostat The thermostat is a special temperature control device for the control of defrosted refrigerated rooms by resistance or for hot gas monitoring and for controlling the operation of the compressor and condenser and evaporator fan motors. Its functions include start and stop time A set of different electromechanical components to prevent overloads in the electrical supply line. It can be electromechanical or electronic. It is a component whose function is to control the room temperature (indoor or outdoor) and keep it as constant as possible. It acts by automatically stopping or starting the compressor, fans or other electromechanical equipment. It usually consists of a bulb, a capillary tube and electrical contacts. Its operation is based on the principle of expansion. The thermostat contains a gas in its capillary, which can be Sulfuric Dioxide, Methyl Chloride and the gas used in the system or a similar gas. The expansion or contraction of the gas molecules transmits movement to a bellows connected to a moving part, which moves by closing or opening the electrical contacts and thus connecting or disconnecting the connected equipment to be controlled. In refrigeration systems, the thermostat must also control the start and stop of the defrosting process by electrical resistance or reverse cycle. Pressure Switch In a continuous process, mechanical cooling would not occur without a liquid (refrigerant) pressure changing throughout the refrigeration cycle. However, when the pressure exceeds certain limits, it can damage some refrigeration components. Pressure switches are used to prevent this from happening. Their main function is to protect the components of the refrigeration cycle from overpressure (higher pressure than acceptable) or underpressure (lower pressure than acceptable) during equipment operation. Pressure switches evaluate the high side pressure (high pressure switch) and the low side pressure (low pressure switch), and in semi-hermetic compressors, they also evaluate the oil pressure. The change in the pressure of the refrigerant level in the cycle makes the electrical contacts of the pressure switch, which can control the fans, alarms, and even the compressor or other elements of the refrigeration cycle. Thermometer
In the cold room, usually outside the insulated panel above the door, an analog thermometer or digital – for measuring and indicating the temperature inside the room. The thermometer can still give a high temperature indicator sound or light alarm. The device has a probe with a cable of about one meter, which allows local positioning for better comfort inside the room. Electrical System The electrical system of the cold/freezer storage room carries all the devices, cables and electrical equipment installed and contributing to the proper operation of the entire set of equipment. In general, the operation of the cold/freezer storage is controlled from a control panel that includes partial protection devices for the compressor motors, the condenser fan, the evaporator fan, the defrosting element and the lighting circuit inside the room. This partial electrical panel is electrically operated via a cable with a cross-section sufficient for the total electrical power of all the installed equipment. The interior lighting of the cold/freezer storage room must provide good visibility of the stored products and must have a switch drive next to the room access door. All devices and electrical cables installed inside the cold/freezer storage room must be of the appropriate class and must be installed in the appropriate technical duct system. Condensate Drain Pipe Diameter of the condensate drain pipe This will allow easy gravity drainage of the condensates produced in the defrosting process of the freezer room and collected in the condensate tray. The condensate can be disposed of directly to the outside or directed to a previously defined condensate collection network, taking into account the need to install traps to prevent unpleasant odors from entering the drainage system. Where these pipes are needed along any wall, they must be properly insulated to prevent the effect of moisture on this infrastructure. In cold storage at temperatures below warm degrees, it is necessary to provide for the installation of a discharge heater element installed along the section of the drain pipes inside the room to prevent the regeneration of condensate.