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temperature profile for cross flow heat exchanger

Here’s a breakdown of the temperature profile for a cross flow heat exchanger, specifically when both fluids are unmixed:

🔥 Cross Flow Heat Exchanger – Both Fluids Unmixed

➤ Flow Arrangement:

  • One fluid flows horizontally (say, hot fluid in tubes).

  • The other flows vertically (say, cold air across the tubes).

  • No mixing within or between the fluids.

📈 Temperature Profile Description:

▪ Hot Fluid:

  • Inlet temperature: High.

  • As it flows, it loses heat to the cold fluid.

  • Outlet temperature: Lower than inlet, but not uniform across the exchanger due to varying contact time.

▪ Cold Fluid:

  • Inlet temperature: Low.

  • Gains heat as it flows across the hot tubes.

  • Outlet temperature: Higher, but also varies across the exchanger.

🌀 Because of the crossflow and no mixing:

  • Each point on the exchanger sees a different temperature gradient, depending on how long each fluid has been in contact with the surface.

  • The temperature distribution is nonlinear and more complex than in counterflow or parallel flow exchangers.

📊 Typical Temperature Profile (schematic layout):

                ↑ Cold fluid in
        │
  High  │       ┌──────────────┐
  Temp  │       │              │
        │       │              │ → Hot fluid in (right side)
        │       │              │
        ↓       └──────────────┘
      Cold fluid out           ← Hot fluid out

⬇ Temperature Curves:

  • Cold fluid gradually heats up — the curve starts low and arcs upward.

  • Hot fluid cools down — starts high and arcs downward.

  • The curves are not parallel, and not symmetrical due to crossflow geometry and varying heat exchange rate.

🔍 Efficiency:

  • The effectiveness depends on the heat capacity ratio and the NTU (Number of Transfer Units).

  • Generally less efficient than counterflow but more efficient than parallel flow.

cross flow heat exchanger with both fluids unmixed

A cross flow heat exchanger with both fluids unmixed refers to a type of heat exchanger where two fluids (hot and cold) flow perpendicular (at 90°) to each other, and neither fluid mixes internally or with the other. This configuration is common in applications like air-to-air heat recovery or automotive radiators.

Key Features:

  • Cross flow: The two fluids move at right angles to each other.

  • Unmixed fluids: Both the hot and cold fluids are confined to their respective flow passages by solid walls or fins, preventing any mixing.

  • Heat transfer: Occurs across the solid wall or surface separating the fluids.

Construction:

Typically includes:

Enclosed channels for the second fluid (e.g., water or refrigerant) to flow inside the tubes.

Tubes or finned surfaces where one fluid (e.g., air) flows across the tubes.

Common Applications:

  • Radiators in cars

  • Air-conditioning systems

  • Industrial HVAC systems

  • Heat recovery ventilators (HRVs)

Advantages:

  • No contamination between fluids

  • Simple maintenance and cleaning

  • Good for gases and fluids that must remain separate

a cross flow heat exchanger used in a cardiopulmonary

A cross-flow heat exchanger in a cardiopulmonary context, such as during cardiopulmonary bypass (CPB) procedures, is a critical component used to regulate a patient’s blood temperature. These devices are commonly integrated into heart-lung machines to warm or cool blood as it’s circulated outside the body during open-heart surgeries or other procedures requiring temporary heart and lung support.

How It Works

In a cross-flow heat exchanger, two fluids—typically blood and a heat transfer medium (like water)—flow perpendicular to each other, separated by a solid surface (e.g., metal or polymer plates/tubes) that facilitates heat transfer without mixing the fluids. The design maximizes heat exchange efficiency while maintaining biocompatibility and minimizing blood trauma.

  • Blood Flow Path: Oxygenated blood from the heart-lung machine flows through one set of channels or tubes.

  • Water Flow Path: Temperature-controlled water flows through an adjacent set of channels in a perpendicular direction, either warming or cooling the blood depending on the clinical need (e.g., inducing hypothermia or rewarming).

  • Heat Transfer: The temperature gradient between the blood and water drives heat exchange through the conductive surface. The cross-flow arrangement ensures a high heat transfer rate due to the constant temperature difference across the exchanger.

Key Features

  1. Biocompatibility: Materials (e.g., stainless steel, aluminum, or medical-grade polymers) are chosen to prevent clotting, hemolysis, or immune reactions.

  2. Compact Design: Cross-flow exchangers are space-efficient, crucial for integration into CPB circuits.

  3. Efficiency: The perpendicular flow maximizes the temperature gradient, improving heat transfer compared to parallel-flow designs.

  4. Sterility: The system is sealed to prevent contamination, with disposable components often used for single-patient procedures.

  5. Control: Paired with a heater-cooler unit, the exchanger maintains precise blood temperature (e.g., 28–32°C for hypothermia, 36–37°C for normothermia).

Applications in Cardiopulmonary Procedures

  • Hypothermia Induction: During CPB, the blood is cooled to reduce metabolic demand, protecting organs like the brain and heart during reduced circulation.

  • Rewarming: After surgery, the blood is gradually warmed to restore normal body temperature without causing thermal stress.

  • Temperature Regulation: Maintains stable blood temperature in extracorporeal membrane oxygenation (ECMO) or other long-term circulatory support systems.

Design Considerations

  • Surface Area: Larger surface areas improve heat transfer but must balance with minimizing priming volume (the amount of fluid needed to fill the circuit).

  • Flow Rates: Blood flow must be turbulent enough for efficient heat transfer but not so high as to damage red blood cells.

  • Pressure Drop: The design minimizes resistance to blood flow to avoid excessive pump pressure.

  • Infection Control: Stagnant water in heater-cooler units can harbor bacteria (e.g., Mycobacterium chimaera), necessitating strict maintenance protocols.

Example

A typical cross-flow heat exchanger in a CPB circuit might consist of a bundle of thin-walled tubes through which blood flows, surrounded by a water jacket where temperature-controlled water circulates in a perpendicular direction. The exchanger is connected to a heater-cooler unit that adjusts water temperature based on real-time feedback from the patient’s core temperature.

Challenges and Risks

  • Hemolysis: Excessive shear stress from turbulent flow can damage blood cells.

  • Thrombogenicity: Surface interactions may trigger clot formation, requiring anticoagulation (e.g., heparin).

  • Air Embolism: Improper priming can introduce air bubbles, a serious risk during bypass.

  • Infections: Contaminated water in heater-cooler units has been linked to rare but severe infections.

How does a counterflow heat exchanger work?

In the counterflow heat exchanger, two neighboring aluminum plates create channels for theair to pass through. The supply air passes on one side of the plate and the exhaust air onthe other. Airflows are passed by each other along parallel aluminum plates instead ofperpendicular like in a crossflow heat exchanger. The heat in the exhaust air is transferredthrough the plate from the warmer air to the colder air.
Sometimes, the exhaust air is contaminated with humidity and pollutants, but airflows nevermix with a plate heat exchanger, leaving the supply air fresh and clean.

The utilization of air-to-air heat exchangers in ventilation and energy-saving engineering

The core function of an air-to-air heat exchanger is to transfer the residual heat carried in the exhaust air (indoor exhaust air) to the fresh air (outdoor intake air) through heat exchange, without directly mixing the two airflows. The entire process is based on the principles of heat conduction and energy conservation, as follows:

Exhaust waste heat capture:
The air expelled indoors (exhaust) usually contains a high amount of heat (warm air in winter and cold air in summer), which would otherwise dissipate directly to the outside.
The exhaust air flows through one side of the heat exchanger, transferring heat to the heat conducting material of the heat exchanger.
Heat transfer:
Air to air heat exchangers are usually composed of metal plates, tube bundles, or heat pipes, which have good thermal conductivity.
Fresh air (air introduced from outside) flows through the other side of the heat exchanger, indirectly contacting the heat on the exhaust side, and absorbing heat through the wall of the heat exchanger.
In winter, fresh air is preheated; In summer, the fresh air is pre cooled (if the exhaust air is air conditioning cold air).
Energy recovery and conservation:
By preheating or pre cooling fresh air, the energy consumption of subsequent heating or cooling equipment is reduced. For example, in winter, the outdoor temperature may be 0 ° C, with an exhaust temperature of 20 ° C. After passing through a heat exchanger, the fresh air temperature may rise to 15 ° C. This way, the heating system only needs to heat the fresh air from 15 ° C to the target temperature, rather than starting from 0 ° C.
Airflow isolation:
Exhaust and fresh air flow through different channels in the heat exchanger to avoid cross contamination and ensure indoor air quality.
technological process
Exhaust collection: indoor exhaust gas is guided to the air-to-air heat exchanger through a ventilation system (such as an exhaust fan).
Fresh air introduction: Outdoor fresh air enters the other side of the heat exchanger through the fresh air duct.
Heat exchange: Inside the heat exchanger, exhaust and fresh air exchange heat in isolated channels.
Fresh air treatment: Preheated (or pre cooled) fresh air enters the air conditioning system or is directly sent into the room, and the temperature or humidity is further adjusted as needed.
Exhaust emission: After completing heat exchange, the exhaust temperature decreases and is finally discharged outdoors.
Types of air-to-air heat exchangers
Plate heat exchanger: composed of multiple layers of thin plates, with exhaust and fresh air flowing in opposite or intersecting directions in adjacent channels, resulting in high efficiency.
Wheel heat exchanger: using rotating heat wheels to absorb exhaust heat and transfer it to fresh air, suitable for high air volume systems.
Heat pipe heat exchanger: It utilizes the evaporation and condensation of the working fluid inside the heat pipe to transfer heat, and is suitable for scenarios with large temperature differences.
アドバンテージ
Energy saving: Recovering 70% -90% of exhaust waste heat, significantly reducing heating or cooling energy consumption.
Environmental Protection: Reduce energy consumption and lower carbon emissions.
Enhance comfort: Avoid direct introduction of cold or hot fresh air and improve indoor environment.

Mine exhaust heat extraction box with built-in air-to-air heat exchanger

The built-in air-to-air heat exchanger in the mine exhaust heat extraction box is a device specifically designed to recover waste heat from mine exhaust air. Mine exhaust refers to the low-temperature, high humidity waste gas discharged from a mine, which usually contains a certain amount of heat but is traditionally discharged directly without being utilized. This device uses a built-in air-to-air heat exchanger (i.e. air-to-air heat exchanger) to transfer heat from the exhaust air to another stream of cold air, thereby achieving the goal of waste heat recovery.

動作原理
Lack of air input: The mine's lack of air is introduced into the heat extraction box through the ventilation system. The temperature of the exhaust air is generally around 20 ℃ (the specific temperature varies depending on the depth of the mine and the environment), and the humidity is relatively high.
Function of Air to Air Heat Exchanger: The built-in air to air heat exchanger usually adopts a plate or tube structure, and the exhaust air and cold air exchange heat through a partition type in the heat exchanger. The heat from the lack of wind is transferred to the cold air, while the two airflows do not mix directly.
Heat output: After being heated by heat exchange, the cold air can be used for anti freezing of mine air inlet, heating of mining area buildings, or domestic hot water, while the exhaust air is discharged at a lower temperature after releasing heat.
Characteristics and advantages
Efficient and energy-saving: Air to air heat exchangers do not require additional working fluids and directly utilize the heat transfer from air to air. They have a simple structure and low operating costs.
Environmental friendliness: By recycling exhaust heat and reducing energy waste, it meets the requirements of green and low-carbon development.
Strong adaptability: The equipment can be customized and designed according to the flow rate and temperature of the mine exhaust, suitable for mines of different scales.
Easy maintenance: Compared to heat pipe or heat pump systems, air-to-air heat exchangers have a relatively simple structure and require less maintenance.
アプリケーションシナリオ
Anti freezing at the wellhead: Use the recovered heat to heat the mine air intake and avoid freezing in winter.
Building heating: providing heating for office buildings, dormitories, etc. in the mining area.
Hot water supply: Combined with the subsequent system, provide a heat source for domestic hot water in the mining area.
precautions
Moisture treatment: Due to the high humidity of the exhaust air, the heat exchanger may face the problem of condensation water accumulation, and a drainage system or anti-corrosion materials need to be designed.
Heat transfer efficiency: The efficiency of an air-to-air heat exchanger is limited by the specific heat capacity and temperature difference of the air, and the recovered heat may not be as high as that of a heat pump system, but its advantage lies in its simple structure.

Rotary heat exchanger manufacturers

There are several well-known rotary heat exchanger manufacturers that provide high-efficiency solutions for HVAC, industrial, and energy recovery applications. Below are some leading companies:

1. Global Rotary Heat Exchanger Manufacturers

✅ Heatex (Sweden) – Specializes in air-to-air rotary and plate heat exchangers for HVAC and industrial applications.
✅ Klingenburg GmbH (Germany) – Offers rotary heat exchangers with advanced coatings for high humidity and corrosive environments.
✅ Seibu Giken (Japan) – Known for its desiccant rotors and energy recovery wheels, ideal for pharmaceutical and cleanroom applications.
✅ FläktGroup (Germany) – Supplies energy-efficient rotary heat exchangers for large commercial and industrial buildings.
✅ REC Air Handling (Netherlands) – Provides customizable rotary heat exchangers for HVAC and industrial heat recovery.

2. China-Based Rotary Heat Exchanger Manufacturers

✅ Hoval – Specializes in plate and rotary heat exchangers for HVAC and industrial processes.
✅ Holtop – Manufactures energy recovery ventilation (ERV) systems with rotary heat exchangers.
✅ Zibo Qiyu – Offers aluminum-based rotary heat exchangers for air handling systems.
✅ Shanghai Shenglin – Produces rotary wheels for air-to-air heat recovery applications.

3. Key Features to Consider

✔ Material – Aluminum, coated surfaces (for corrosion resistance), or desiccant-coated wheels (for humidity control).
✔ Efficiency – High heat recovery efficiency (up to 85%) for energy savings.
✔ Application – Industrial HVAC, cleanrooms, pharmaceutical, or general ventilation.
✔ Customization – Size, coatings, and integration with existing systems.

Kiln waste heat recovery and reuse system - gas stainless steel cross flow heat exchanger scheme

The kiln waste heat recovery and reuse system aims to fully utilize the high-temperature heat in the kiln exhaust gas, and achieve a win-win situation of energy conservation and environmental protection through gas stainless steel cross flow heat exchangers. The core of this solution lies in the use of a stainless steel cross flow heat exchanger, which efficiently exchanges heat between high-temperature exhaust gas and cold air, generating hot air that can be reused.

Working principle: The exhaust gas and cold air flow in a cross flow manner inside the heat exchanger and transfer heat through the stainless steel plate wall. After releasing heat from exhaust gas, it is discharged. Cold air absorbs the heat and heats up into hot air, which is suitable for scenarios such as assisting combustion, preheating materials, or heating.

Advantages:

Efficient heat transfer: The cross flow design ensures a heat transfer efficiency of 60% -80%.
Strong durability: Stainless steel material is resistant to high temperatures and corrosion, and can adapt to complex exhaust environments.
Flexible application: Hot air can be directly fed back to the kiln or used for other processes, with significant energy savings.
System process: Kiln exhaust gas → Pre treatment (such as dust removal) → Stainless steel heat exchanger → Hot air output → Secondary utilization.

This solution is simple and reliable, with a short investment return cycle, making it an ideal choice for kiln waste heat recovery, helping enterprises reduce energy consumption and improve efficiency.

ZiBo QiYu manufacturer

ZIBO QIYU AIR CONDITION ENERGY RECOVERY EQUIPMENT CO., LTD. We have kinds of air to air heat exchangers, such as AHU, HRV, heat tube heat exchangers, rotary heat exchangers, steam heating coil, surface air cooler.

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Website:https://www.huanrexi.com

Application of Air-to-Air Heat Recovery Exchanger in Livestock Ventilation

The Air-to-Air Heat Recovery Exchanger plays a vital role in the livestock ventilation industry by enhancing energy efficiency and maintaining optimal indoor conditions. Designed to recover waste heat from exhaust air, this exchanger transfers thermal energy from the warm, stale air expelled from livestock facilities to the incoming fresh, cooler air without mixing the two streams. In poultry houses, pig barns, and other breeding environments, where consistent temperature control and air quality are critical, it reduces heating costs in winter by pre-warming fresh air and mitigates heat stress in summer through effective thermal regulation. Typically constructed with corrosion-resistant materials like aluminum or stainless steel, it withstands the humid and ammonia-rich conditions common in livestock settings. By integrating into ventilation systems, the exchanger not only lowers energy consumption but also supports sustainable farming practices, ensuring animal welfare and operational efficiency. Its application is particularly valuable in large-scale breeding operations aiming to balance cost-effectiveness with environmental responsibility.

Air-to-Air Heat Recovery Exchanger

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