Hot gas defrost diagram

Hot gas defrost piping in cases About Press Copyright Contact us Creators Advertise Developers Terms Privacy Policy Safety How YouTube works Test new features 2021 Google LLC. Usually require one or two defrost peri-ods per day.

The pressure in the evaporator is 6 to 7 bar 87 to 102 psi and the pressure in the wet return line is 05 to 1 bar 7 to 14 psi which create a differential pressure of.

Hot gas defrost diagram. This document reviews standard hot gas defrost piping diagrams for recirculated controlled pressure receiver CPR direct expansion and gravity flooded evaporator systems. This document reviews standard hot gas defrost piping diagrams for recirculated controlled pressure receiver CPR direct expansion and gravity flooded evaporator systems. The hot gas defrost process.

First when the hot gas valve is sud-denly opened and any condensate in the hot gas line or residual cold liquid in the coil is propelled by the high-pressure vapor. Second is at the conclusion of defrost when liquid conden-sate inside the coil. E Time Delay Hot gas cycle Must be set at least for two minutes up to 5 min in order to i pump out all remaining refrigerant in the evapora-tor and ii Pre-heat the drain pan prior to the hot gas entering the coil.

This timer setting must be longer than the compressor anti-short cycle set-ting if equipped. In the hot gas defrost process. First when the hot gas valve is suddenly opened and any condensate in the hot gas line or residual cold liquid in the coil is propelled by the high-pressure vapor.

Second is at the conclusion of defrost when liquid condensate inside the coil. The frost ice is melted using the latent heat of condensation of hot gas. So hot gas first cools itself to 50 deg F.

Then it condenses to liquid releassing latent heat of condensation. This heat melts the ice. The heat transfer is very uniform and very very efficient as it is using the full surface area of the evaporator.

Having said this let us also understand hot gas defrost is more complicsted than this. Hot Gas Defrost Techniques Reverse Flow o Typically on Rack Systems o Hot Gas is directed from Compressor Discharge or Liquid Receiver to Outlet of Evaporator o Gas flows backwards through Evap and condensed liquid is directed to liquid lineheader. When the defrost process is completed the evaporator pressure is equal to defrost pressure.

The pressure in the evaporator is 6 to 7 bar 87 to 102 psi and the pressure in the wet return line is 05 to 1 bar 7 to 14 psi which create a differential pressure of. 55 bar 80 psi. To avoid pressure shocks.

Authors suggest opportunities to improve controls for hot gas defrost systems. The article describes hot gas defrost for ammonia systems indicating special requirements for CO 2 plants where relevant. Some of those requirements are derived from higher pressures and higher pressure differentials with CO 2.

The article indicates that when defrost is performed in an optimal way could save up to. There are two basic types of gas defrosts. Hot gas defrost is where superheated discharge gas is directed into the evaporator and Kool gas is a trademarked name for a defrost that directs saturated vapor from the top of the receiver unto the evaporator.

Each has advantages and disadvantages but both work essentially the same way. GAS DEFROST Gas defrost uses the systems internal energy to defrost the evaporator utilizing the naturally occurring high temperature discharge vapour to add the necessary heat required to accomplish the defrost cycle. Through the years refrigeration systems have employed several different methods for introducing the hot gas to the evaporator.

Hot Gas Bypass HGBP and the Pressure Enthalpy Diagram. Hot gas bypass also called discharge bypass is a feature in a refrigeration system uses to satisfy the mechanical needs of the system during low load conditions. Low load conditions can lead to frosting or freezing the evaporator refrigerant flood back to the compressor system.

Used to control a hot gas defrost process. Hot Gas Defrost Control Groups Figure 1 presents a typical industrial refrigeration evaporator with hot gas defrost. Control valves for the evaporator could be divided in the 4 main groups.

Pumped liquid feed to the evaporator. This valve train typically. Defrost Control Board Wiring Diagram wiring diagram is a simplified welcome pictorial representation of an electrical circuit.

It shows the components of the circuit as simplified shapes and the facility and signal connections in the middle of the devices. Usually require one or two defrost peri-ods per day. Has many vari-eties all of which utilize a compressed vapor in the evaporator coil.

Some systems utilize the latent heat of con-densation of this compressed vapor as a. Time graph for time clock defrosting. Use 70F with electronic defrost sensor.

The diagram shows the location for each defrost type that uses a klixon. NOTE The termination klixon 5535 Settings for electric defrost is located in the right hand end of the upper electrical raceway. The termination klixon for gas defrost is located next to the rear coil bypass check valve.

HOT GAS BYPASS VALVE GENERAL The Hot Gas Bypass System design consists of two important modifications to the standard air conditioning unit. Each of these sets of controls perform a specific function but both are necessary and dependent upon one another in the overall operation of the. Gas Defrost Split Suction Water Lines 1 12 ID Suction Line.

2 3 or 4 compressors 1 38 OD 5 or 6 compressors 1 58 OD Liquid Line 78 OD Sat. Suction 78 OD Gas Defrost 58 OD Split Suction 1 38 OD Suction Liquid Line Water Outlet Sat. Suction Gas Defrost Water Inlet 30 12 25 22 12 14 19 34 21 38 30 12 26 12 26 12.

A hot gas defrost refrigeration system has a compressor a condenser a receiver an evaporator interconnected by fluid passage means and incorporating valve means to cause refrigerant to flow sequentially through the compressor condenser receiver and evaporator to the compressor during the refrigeration cycle. Hot Gas Defrost. Concisely the hot gas defrost method uses the naturally occurring high-temperature refrigerant vapor from the discharge side of the compressor to warm the evaporator coil and melt the ice accumulated on it.

Although the basic concept of hot gas defrost is pretty straightforward three different methods for introducing hot gas. R22 PH Diagram Diagram created using REFPROP NIST Reference Fluid Properties As can be seen the critical point of R-22 is more than 200F placing it well above the operating conditions of typical refrigeration systems. This can be contrasted with the CO 2 PH diagram with a critical point of 88F.

Strap a thermocouple to the refrigerant line outlet of the hot gas bypass valve as illustrated in Figure 1. Connect a set of refrigerant gauges to the suction and discharge service ports of the compressor system. The suction pressure will be used to monitor the bypass activation point which is.

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