Direct refrigeration system

Manojkumar Ashok Maurya

ME13906

Heat-power engineering

Date: 11/02/2014

Guided by:Prof. (Dr.) Mandar Lele

Introduction

• Direct refrigeration also known as DX(direct expansion) system

• System in which the cooling effect is obtained from the expansion of liquid refrigerant into vapor

• The refrigerant is used to directly transport heat from the space to be cooled to the space where heat is released

• The heat from the cooling object is taken up in the evaporator and released in the condensor

Continued…

• It has a 4 main component evaporator, compressor, condensor and expansion valve

• Direct expansion system is common term applied to system working on vapour compression refrigeration cycle

Basic layout of direct system

Basic layout of VCRS

The adjacent figure shows basic layout of VCRS which is similar to Direct refrigeration system

T-S diagram

Direct system for supermarket refrigeration

• The refrigerant circulates in the machine room where the compressor is placed, to the cooling cabinets where the refrigerant evaporates

• It uses long tubes between the compressor, cooling cabinets and condensor on the roof, leading to high refrigerant charges

• Multiplex system is the most common type of direct system• Here, several compressors are connected in parallel and

connected to a common tube both on low pressure side and high pressure side

• Another direct system uses only one compressor connected to one or more cabinet

Continued…

Applications

Application Description Refrigerant

Domestic Food appliances R-600a, R-134a

Commercial Fresh and frozen food in retail outlet

R-134a, R-404A, R-507

Electronic cooling Used in large computers and CMOS circuitry

R-134a, R-404A, R-507

Transport refrigeration To preserve food during transportation

R-134a, R-407C, R-410A

Advantages

• Mature technology• Relative inexpensive• Can be driven using mechanical energy or

with electrical energy• Efficient up to 60% of Carnot's theoretical

efficiency

Thank you