Calculation and selection of a refrigeration machine for a distribution refrigerator in the city of Novosibirsk

Contents

Introduction

Objectives and objectives of the course project

Thermal calculation of refrigerating machine

Design temperature mode of refrigerating machine

Thermal calculation of the refrigerating machine. Calculation and selection of compressors

Calculation and selection of heat exchange equipment

Calculation and selection of capacitor

Calculation and selection of chamber cooling devices

Calculation and selection of auxiliary equipment

Calculation and selection of receivers

Calculation and selection of oil separator and oil collector

Calculation and selection of intermediate vessel

Selection of deaerator

Calculation and selection of pumps

Cooling tower calculation and selection

Piping Calculation

Description of refrigeration machine diagram

Conclusion

List of sources used

Appendix A-Operation of refrigeration equipment

Appendix B-Schematic symbols

Appendix B - Refrigeration Unit Diagram

Introduction

A refrigerator is a building structure or device designed to cool, freeze and store food products usually at temperatures below ambient temperature.

The refrigerator has certain features due to its functions. Air temperature, relative humidity and air circulation speed shall be maintained in the refrigerator compartments. Refrigerators are subject to high sanitary requirements. Space-planning solutions of refrigerators shall comply with the requirements of SNiP - 105-74 and "Standards for process design of refrigerators."

Distribution refrigerators are designed to provide cities and industrial centers with seasonal food products evenly throughout the year. Distribution refrigerators are characterized by a large capacity of food storage rooms.

Distribution refrigerators are universal and specialized (for meat, fish, fruits, etc.). Distribution refrigerators often include ice cream, water and dry ice shops, workshops for packing and freezing fruits and vegetables, as well as for packing oil, meat and other products. Such enterprises are called cold processing plants.

Distribution refrigerators are independent enterprises with the rights of a legal entity, a complete accounting and reporting system with an independent balance sheet.

Distribution refrigerators and refrigeration plants are managed by the Ministry of Trade of the Union Republics. The work of refrigeration enterprises of the RSFSR is led by the republican office of Rosmyasorybtorg.

Novosibirsk Cold Processing Plant is the main and largest logistics center outside the Urals for the processing, storage and sale of food products (regime cargoes). The main purpose of our warehouse complex has always been to meet the needs of the state reserve.

Novosibirsk Cold Processing Plant cooperates with more than 100 companies that store various types of goods: oil, ice cream, meat products, fish products, dairy products, deep freezing products, various canned food, preserves, preservatives, vegetables, fruits, and category "C" products.

To implement the design of the distribution refrigerator, it is necessary to calculate and select the refrigeration equipment, to develop a schematic diagram of the refrigeration unit.

Objectives and objectives of the course project

Purpose of the course project :

- application of acquired knowledge on calculation and selection of main and auxiliary refrigeration equipment ;

- design of the refrigeration unit diagram.

Course Project Tasks:

- development of self-work skills;

- application of legislative, regulatory and design documentation to solve technical issues;

-provision of data analysis skills and their systematization,

obtained from educational and periodical literature.

Job to run the course project

Calculation and selection of refrigerator for distribution refrigerator:

- refrigerant boiling point: t01 = 10 0С; t02 = 30 0C; t03 = 40 oC;

- cooling capacity, respectively: Q01 = 320 kW; Q02 = 220 kW; Q03 = 110 kW;

- type of condenser - evaporative;

- city - Novosibirsk.

Thermal calculation of refrigerating machine

The tasks of the thermal calculation of the refrigerating machine are:

- determination of required volume capacity of the compressor;

- compressor selection;

- determination of power consumption;

-determination of heat load on the condenser.

Initial data for thermal calculation:

- required cooling capacity of the machine, accepted equal to the thermal load on the compressor;

-computed temperature mode of the refrigerating machine;

-computed diagram of the refrigerating machine.

Calculation and selection of auxiliary equipment

The calculation and selection of the auxiliary equipment of the refrigerating machine depends on the circuit of the liquid refrigerant supply unit to the evaporation system. The circuits of the refrigerant supply unit to the cooling devices are separated according to the supply method, i.e., depending on the pressure of the liquid ammonia supplied to the chamber equipment.

Three supply methods are distinguished: under the influence of the pressure difference of condensation and boiling (rp0); under the head of the hydrostatic liquid column; under the pressure generated by the pump. The first two methods form a group of pump-free circuits, the third - a group of pump-circulating circuits.

The chambers are cooled by a two-stage ammonia refrigerator by two boiling points with a fixed intermediate pressure and a pumping circulation system for supplying refrigerant to the chambers.

Depending on the cooling system chosen (direct), receivers (circulation, linear, drain), intermediate vessel, oil separator and oil collector, centrifugal pumps for liquid coolant supply and for cooling water supply to condenser and compressors, cooling water cooling device shall be included in the cooling unit circuit (pumping circulation).

Description of refrigeration unit diagram

For the designed refrigeration plant of the meat processing plant, a two-stage scheme for three boiling points (t01=10oC, t02=-30oC, t03=40oC) with a fixed intermediate pressure and an upper supply of coolant (ammonia) to the cooling chambers (air coolers) was adopted.

In the above diagram of a two-stage cooling plant for three boiling points, three screw single-stage compressor units for the corresponding boiling points are used:

t01 = 10 0C A28073 brands;

t02 = 30 0C A35073 brands;

t03 = 40 0C A28073 brands.

In addition to compressors, the following are also installed:

drainage horizontal receiver of a standard size 2.5RD ;

linear horizontal receiver of 1.5WP size;

circulation vertical receiver of 1.5WP size;

intermediate vessel of a standard size 120PSz;

oil separator of size 100MA;

oil pan of a standard size 60MZS ;

Refrigerant vapors are sucked from CP40 and CP30 by low pressure screw compressors, where it is compressed from boiling pressure to condensation pressure, then passes through oil separators and is pumped into an intermediate vessel. Steam passes through the liquid coolant layer and is cooled while in the MS at intermediate temperature and pressure. After that, the high-pressure screw compressor sucks steam from CP10 and the PS in it is compressed from the intermediate pressure to the condensation pressure, passes through the oil separator, after the oil separator, the steam passes to the common oil separator and is pumped to the evaporation condensers. In each oil separator, the refrigerant vapor is separated from the oil. Evaporation condensers remove heat from refrigerant and after air conditioning, and consume minimum amount of energy and water. They combine a cooling tower and a cooling condenser in one unit. A small part of the water evaporates, removing heat from the refrigerant and condensing it inside the heat exchanger. The formed liquid ammonia is drained into the linear receiver, and from it it goes to the manifold of the distribution station.

One part of coolant is supplied to CP10 and the other to intermediate vessel. Note here that majority of coolant is fed into PS coil while smaller portion is throttled in control valve from condensation pressure to intermediate pressure and fed into PS to maintain constant coolant level therein.

As a result of heat exchange with the liquid in the intermediate vessel, the liquid in the coil is cooled to a temperature close to the intermediate one. So that there is no mixing of liquid flows with different temperatures, the supercooled liquid from the coil is supplied to CP30 and CP40. Before TsR10, TsR30 and TsR40 coolant drosselirutsya in the regulating gate from condensation pressure up to the boiling pressure.

Of all circulation receivers RTs10, RTs30, RTs40, liquid coolant is supplied by centrifugal pumps of AG type to the liquid header, where it is distributed to cooling devices.

In the cooling devices, the liquid coolant boils, taking heat from the products, and the unspoiled vapor-liquid mixture formed during boiling returns through the steam header to the circulation receivers RTs10, RTs30, RTs40. The vapor-liquid mixture is separated by the receiver into steam and saturated liquid.

From circulation receivers RTs10, RTs30, RTs40, refrigerant vapors are sucked by screw single-stage compressor units according to their corresponding boiling points and the cycle is repeated.

Hot refrigerant vapors are used to thaw air cooler batteries.

To this end, the scheme provides a pipeline for supplying hot vapors from the delivery line to the thawing collector OK, through which hot vapors can be directed to any chamber.

A drain horizontal receiver is installed to collect the formed liquid coolant. Fluid is supplied to the drain receiver through the drain header.

An oil collector is provided in the diagram for oil drain from the compressor and refrigerating machine devices. In order to reduce pressure in oil collector, it is connected to suction line of single-stage screw compressor unit. The oil is discharged into the tank and sent for regeneration.

The production of air is made from condensers and a linear receiver via the automatic AB4 air separator.

Conclusion

As a result of the performed work, optimal placement of refrigeration equipment for district cold supply was carried out during heat treatment of products, as well as storage of cooled and frozen products in cooled rooms (chambers) of the distribution refrigerator.

In order to increase the economic efficiency of refrigeration units, the scheme used modern equipment, which allows to automate the refrigeration unit and creates favorable working conditions for service personnel.

Evaporative condenser is selected to remove condensation heat.

Suspended air coolers of AVP type with transverse-spiral finning are installed in product storage chambers.

In the air coolers of this row, the flow of cold air is directed horizontally to two opposite sides; this ensures "calm," with low speed of movement, air supply and uniform field of its speeds. The use of these devices allows to reduce weight loss from drying.

The course project of the refrigerating machine of the distribution refrigerator in the city of Novosibirsk for three boiling points was carried out in accordance with modern requirements for the design of industrial refrigerators.