Heat Sink Temperature Research Articles

Dynamic simulation and control of dual-evaporator compression refrigeration systems

The need for refrigeration cooling at two different sub-ambient temperature levels is an important problem in some processes. A modern grocery store is an extremely important global example in which there is a need for a moderate temperature heat sink (5 °C) to keep food cool but also a need for a significantly colder heat sink (− 20 °C) for frozen food products. If the two temperatures are not too different, a single refrigerant can be used. The compression refrigeration configuration then consists of two compressors operating in parallel, a single condenser, a single refrigerant liquid surge drum and multiple evaporators. Liquid refrigerant at high pressure is split into a large number of parallel streams to feed individual evaporators in the cooling and freezing compartments. This paper studies how this multi-variable interacting dynamic system can be modeled and controlled using simple conventional controllers.

HEAT TRANSFER ANALYSIS ON BASE OF HEAT SINK WITH UNIFORM HEAT GENERATION

The present work describes the important results of problem of combined conduction, convection and radiation from a rectangular heat sink base subjected to uniform internal heat generation in its base. The governing equations for temperature distribution within the base are obtained by a relevant energy balance between rate of heat generation, heat conducted, convected and radiated. The derived non-linear partial differential equations are converted into algebraic form using finite difference method with 2nd order accuracy. The obtained algebraic equations have been solved simultaneously by Gauss-siedel iterative method with stringent convergence criteria and a C code has been written for above purpose. The computational domain has been discretized uniformly in all directions. A grid convergence test has been carried out to optimize the size of element. A complete parametric study has been carried out to study the effect of material of heat sink, regime of convection and role of radiation on local temperature distribution and maximum heat sink base temperature. It has been observed that material with high conductivity decreases the local temperature gradient and thus the maximum temperature. The regime of convection has a great influence on maximum temperature of heat sink with 15K of drop in Tmax. for a change in flow regime from free convection to forced convection. A special study on exclusive role of convection on maximum temperature reveals that one should not ignore the role forced convection in heat dissipation. Key Words: Heat generation, Multimode heat transfer, Radiation

Impact of the Regulation Strategy on the Transient Behavior of a Brayton Heat Pump

High-temperature heat pumps are a key technology for enabling the complete integration of renewables into the power grid. Although these systems may come with several variants, Brayton heat pumps are gaining more and more interest because of the higher heat sink temperatures and the potential to leverage already existing components in the industry. Because these systems utilize renewable electricity to supply high-temperature heat, they are particularly suited for industry or energy storage applications, thus prompting the development of various demonstration plants to evaluate their performance and flexibility. Adapting to varying load conditions and swiftly responding to load adjustments represent crucial aspects for advancing such systems. In this context, this study delves into assessing the transient capabilities of Brayton heat pumps during thermal load management. A transient model of an emerging prototype is presented, comprising thermal and volume dynamics of the components. Furthermore, two reference scenarios are examined to assess the transient performance of the system, namely a thermal load alteration due to an abrupt change in the desired heat sink temperature and, secondly, to a sudden variation in the sink mass flow rate. Finally, two control methodologies—motor/compressor speed variation and fluid inventory control—are analyzed in the latter scenario, and a comparative analysis of their effectiveness is discussed. Results indicate that varying the compressor speed allows for a response time in the 8–20 min range for heat sink temperature regulation (first scenario). However, the regulation time is conditioned by the maximum thermal stress sustained by the heat exchangers. In the latter scenario, regulating the compressor speed shows a faster response time than the inventory control (2–5 min vs. 15 min). However, the inventory approach provides higher COPs in part-load conditions and better stability during the transient phase.

Energy influence of the internal heat exchangers placement in a cascade refrigeration plant. A theoretical and experimental analysis

This paper deals with the analysis of the internal heat exchanger (IHX) impact on the energy performance of a cascade refrigeration plant (CRS) made up of two vapor compression cycles. Three IHX locations have been considered, the first one in the high temperature cycle (HTC), the second one in the low temperature cycle (LTC), and the third one thermally connecting the suction line of the LTC with the liquid line of the HTC. Additionally, five refrigerant pairs R134a/R744, R290/R744, R1270/R134a, R600a/R744, and R1234ze(E)/R744 and three different heatsink temperatures: 293 K, 303 K and 313 K have been considered. The experimental results, obtained in a CRS experimental facility, are contrasted with those obtained from a theoretical model. While theoretical results predict that the IHXs have mainly negative or neglecting effects on the energy performance of the CRS, the experimental ones results show that regardless of location and operating conditions, the activation of an IHX generally improves the COP, up to 5.6 % as a maximum improvement.

Modeling, thermodynamic performance analysis, and parameter optimization of a hybrid power generation system coupling thermogalvanic cells with alkaline fuel cells

During the operation of alkaline fuel cells (AFCs), a significant amount of waste heat is generated, which has negative impacts on energy utilization and the environment. To improve energy efficiency, cost savings, environmental sustainability, and industrial practices, an effective approach is proposed to employ thermogalvanic cells (TGCs) for electric power generation by harvesting low-grade exhaust heat produced in AFCs. A mathematical model of the AFC-TGC hybrid system is established, taking into account the three overpotential losses in AFCs and the irreversible heat losses in TGCs. Based on this thermal-electric coupled model, we investigate the hybrid system’s output performance characteristics and optimal parameter design. The calculated results indicate that the hybrid system achieves a considerable increase of 19.72% in maximum power density from 247.07 W m−2 to 295.80 W m−2 and 5.71% in conversion efficiency from 10.16% to 10.74% compared to a single AFC, respectively. In addition, the output performance of the hybrid system can be further improved by adjusting system parameters such as the AFC’s operating temperature, the length of each TGC cell, the heat sink temperature, and the thermal convection coefficient. More importantly, a comparative study of the maximum power density of AFC-based cogeneration systems reveals that the TGC demonstrates a remarkable ability to economically recover waste heat from the AFC, surpassing previously reported thermal energy utilization devices. This study provides important theoretical guidance for the optimal design and parametric analysis of AFC-TGC hybrid systems, thereby facilitating the development of high-performance energy cascade utilization systems based on AFC devices.

Experimental investigation of forced convective heat transfer and fluid flow in a mini heat pipe with rectangular micro grooves

In the present study, the convective heat transfer coefficient of water in a laminar flow regime under constant inlet temperature conditions inside a flat mini heat pipe was investigated ex-perimentally. Heat flux ranged from 20-50W and various horizontal heat sink temperatures (operating temperature) ranged from 15-35°C with liquid flow rate (3.563E-8 m3/sec) used during the experiments. The rectangular microchannels performance is evaluated in terms of the temperature profile, heat transfer coefficient, Nusselt number and thermal resistance. The results emphasized that the mini heat pipe temperature gradients are less than the tempera-ture of the copper plate and the heat resistance gradually decreases to its lowest value when the heat flux value reaches its highest value if it does not exceed the capillary limits. The data also demonstrated that the coefficient of heat transfer in the condensation zone is lower than in the evaporation zone at different heat sink temperatures. The augmentation rate for the flat mini heat pipe thermal conductivity reached about 240% at a heat load 30W for the positions of thermosyphon and horizontal, while the rate of increase in the case of the anti-gravity situ-ation at a heat load 30W reaches 210%, then the improvement percentage begins to decrease to 200%. A generalized regression equation is developed for the estimation of the Nusselt number valid for water in a flat mini heat pipe.

A computational method to study heat transfer in a helicopter turboshaft engine compartment for waste energy recovery purposes

It is important to take action to make aviation more energy-efficient and less pollutant. One of the approaches currently under development is waste energy recovery. This would be specially advantageous in turboshaft engines, which present an exhaust flow that is not being used for propulsive purposes and with high thermal residual energy that increases infrared signature of helicopters.To evaluate where to locate waste energy recovery devices such as thermoelectric generators or organic Rankine cycles the following is needed: temperatures of exhaust gas flow temperature and exhaust ducts wall temperature, i.e. hot source temperature, and engine compartment temperature, i.e. heat sink temperature. This variables are usually not known beforehand. The present paper develops a method that, with minimal data input, translates flight conditions and engine operation into conditions inside the engine compartment that are later applied to obtain heat transfer in the exhaust ducts, where the waste energy recovery should take place to minimize the influence on the engine. The procedure is based on an algorithm that uses Computational Fluid Dynamics (CFD) simulations validated with experiments.The main findings of this work are: (i) cruise flight velocity has minimal impact on engine compartment temperatures, but hover operation increases it by 5–16 K, (ii) cruise altitude significantly affects engine compartment temperature, with a 12 K difference between 2500 ft and 10000 ft, (iii) considering only the axial component of velocity in exhaust ducts may underestimate wall temperature, (iv) heat transfer in exhaust ducts can be estimated using empirical correlations for natural convection, multiplied by a specific factor, (v) non-invasive methods can recover 23.6 to 31.2 kW of heat from exhaust duct walls, potentially converting up to half of it into useful work.

Thermohydraulic performance analysis and parameters optimization of the combined heat sinks with microchannels and micro pin-fins

The combined heat sinks of microchannels and micro pin-fins are numerically studied in depth by three-dimensional conjugate heat transfer models for flow rate (Qv) ranging from 18 to 90 ml/min. The influence degrees of multiple parameters, i.e., the lengths and widths of the cavities and pin-fins, on cooling effect, pressure drop and comprehensive performance are analyzed quantitatively by Taguchi method. And the optimal combination structures for temperature of heat sink (OCS-T), pressure drop (OCS-PD) and performance evaluation criterion (OCS-PEC) are obtained accordingly. The original heat sink with fan shaped cavities and diamond pin-fins (FC-DPF) and the smooth rectangular heat sink (SR) are selected for comparison. The coupling effects of four structure parameters on the local and average thermal hydraulic characteristics are elucidated. The interrelation of multiple physical fields and the comprehensive efficiency of the optimal combination structures are discussed thoroughly. Moreover, the thermodynamic properties and irreversibility are illustrated based on the entropy generation. Results demonstrate that the length of fan shaped cavity and the width of diamond pin–fin have a dominant impact on heat dissipation and pressure drop. The width of cavity has a noticeable impact on the overall performance. Large width of cavity is favorable to induce transverse flow, and large width of pin–fin contributes to distinct vortices. The symmetrical vortices in the direction of channel height can improve chaotic mixing and temperature uniformity. At high flow rate, the performance evaluation criterion (PEC) of the OCS-PEC is increased by 29 % compared to the original structure FC-DPF. When total thermal resistances of the above two heat sinks are similar (0.43 K/W of the OCS-PEC and 0.45 K/W of the FC-DPF), the pumping power of the OCS-PEC (0.47 W) is 35 % lower than that of the FC-DPF (0.72 W) proving the excellent overall efficiency. In addition, the OCS-PD and OCS-PEC show better thermodynamic performance and less irreversible loss for high flow rate, which implies the energy efficiency advantage. The synergistic mechanism of flow and heat transfer is revealed and the results are significant for further understanding the rules of performance enhancement. The excellent overall performance of the OCS-PEC at high flow rate makes it more promising in application for electronic chips cooling in aerospace, defense and communication fields, thermal management of battery, hydrogen storage, fusion energy management, etc.

Experimental study on an integrated system of thermosyphon loop and vapor compression assisted with phase change material for pulse heat load

In order to safely and energy-efficient handle the pulse heat load of avionics, the paper proposes an integrated system of thermosyphon loop and vapor compression cycle, especially assisted with phase change material (PCM). Under low heat load and heat sink temperature, the system operates as a thermosyphon loop (TL) for energy saving; otherwise as a vapor compression cycle (VCC) for safety. A prototype of the integrated system was developed, where a whole three-dimensional (3D) printed structure worked as the evaporator of the system, consisting of a mini-channel cold plate and a high thermal-conductivity matrix containing PCM. The dynamic performance of the proposed system has been experimented under different pulse heat loads and heat sink temperatures, and compared to the integrated system without PCM and a traditional VCC. The proposed system can handle a peak heat load of 1000 W for 120 s without running the compressor, saving 100 % energy compared to traditional VCC. The PCM enhances both the safety and energy efficiency of the integrated system. On the one hand, it reduces wall temperature during the transition from TL to VCC, avoiding overheating issue. On the other hand, it reduces the operating time of VCC, which is more significant with lower peak heat load and heat sink temperature. Overall, the integrated system assisted with PCM is a promising solution for solving pulsating heat loads.

Parallel connected natural circulation loops using different working fluids: experimental results

Natural Circulation Loops (NCLs) are closed-loop systems that transport heat from a source to a heat sink without a pump, relying on free convection of the working fluid. Previous research has focused on the stability and influence of different operative parameters on NCLs. This experimental study investigates the thermo-hydraulic performance of three parallel-connected NCLs with small inner diameters using three different working fluids: deionized water, glycol aqueous solution (50+50% wt), and FC-43 dielectric fluid. This study examines the steady-state behaviour of the NCLs at various heat sink temperatures and heat powers. The results indicate that the common one-dimensional model for a single loop’s steady-state can be applied to this configuration and for all the tested fluids, and a proposed figure of merit can describe the working fluids and predict their steady-state behaviour.

Experimental research on off-design characteristics of heat pump water heater using low GWP zeotropic blend

Based on the test setup of instant heat pump water heater (IHPWH), the performances of system operating with zeotropic natural mixture (ZNM) (R744/R290 (12/88)) and system operating with R22 refrigerant were compared under variable entry temperature of heat sink (ETHSK) and variable entry temperature of heat source (ETHSC) conditions, aiming to comprehensively evaluate the replacement potential of ZNM in the IHPWH. The results revealed that ZNM had an obvious alternative advantage, mainly attributed to that system operating with ZNM refrigerant achieved the comparable or markedly superior heating capacity and COP and markedly lower discharge temperature compared to those of system operating with R22 refrigerant under two conditions. The discharge temperature of system operating with ZNM refrigerant was reduced by 5.4~26.7? compared to that of system operating with R22 refrigerant, thus system operating with ZNM refrigerant can produce higher temperature domestic hot water. Compared with those of system operating with R22 refrigerant, both heating capacity and COP of system operating with ZNM refrigerant had markedly different trends with the change of ETHSK, while they had slightly different trends with the change of ETHSC. Compared to the ETHSK, the ETHSC has a more conspicuous impact on the heating capacity, COP and discharge temperature of system operating with ZNM refrigerant.

Thermal management of Li-ion batteries in electric vehicles by nanofluid-filled loop heat pipes

An analytical model is developed to determine the thermal performance of a Loop Heat Pipe filled (LHP) with copper oxide–water and alumina–water nanofluids for battery thermal management in electric vehicles. The thermal performances of the LHP are predicted for different heat loads and nanoparticle concentrations. It is demonstrated that for fast charging operation corresponding to a heat load of 150 W, the LHP ensures evaporator temperatures of less than 60 °C for a heat sink temperature of 40 °C. The heat transport capacity of the LHP is enhanced and the evaporator temperature is deceased by augmenting the nanoparticle concentration. The water–CuO nanofluid-filled LHP performs better than the water–Al2O3 nanofluid-filled one. The addition of the nanoparticles increases the LHP total pressure drop and the driving capillary pressure. The capillary limit of the water–CuO nanofluid-filled LHP is hardly affected by CuO nanoparticle concentration until 6% beyond which the capillary limit starts decreasing. For the water–Al2O3 nanofluid-filled LHP, the capillary limit decreases when Al2O3 nanoparticle concentration increases. Beyond 6% Al2O3 nanoparticle concentration, the capillary limit of the Al2O3-filled LHP becomes lower than the water-filled one.

Heat dissipation effects of different nanocoated lateral fins: An experimental investigation

Electrical batteries, mobile phones, central processing units of computing systems, and scientific instruments lose life due to improper heat transfer. Thermal management enables these electronics to run smoothly. This experiment measures heat sink temperature fluctuations during heating and cooling using lateral fins coated with graphene and carbon CNT. The study examined 15 W, 25 W, 35 W, and 45 W heat inputs to record the time to reach 40?C, 50?C, and 60?C. Regardless of the coating material used in the heat sink, the time taken by the heat sinks to attain 60?C was more than 3000 seconds. Heat input reduced the time to below 3000 seconds. Heat sinks dissipated heat until 32?C during cooling. Infrared spectroscopy showed fins and heat sinks? energy retention. Convective heat transfer cooled the middle row of fins, and coated and uncoated heat sinks were evaluated for enhancement ratio. Coating the heat sink with graphene resulted in an enhancement in heat transfer by 1.15. While heating at 15 W, the CNT coated heat sink exhibited a 1.9 enhancement ratio. The graphene-coated heat sink had an enhancement ratio for 25 W, 35 W, and 45 W heat inputs. The study found that operating temperature, input energy, and nanocoatings affect heat sink performance. This work can help optimise heat transfer from the heat sink to the atmosphere by determining nanocoating thickness. Mixed-material coating studies can disclose heat sink performance.

Environmental compatibility and economic feasibility of ground source heat pumps in tropical Asia regarding lifecycle aspects: A case study in Bangkok, Thailand

Ground source heat pumps (GSHPs) in tropical regions require a large-scale ground heat exchanger (GHE) owing to the excessive cooling load and high subsurface temperatures, resulting in increased initial costs and greenhouse gas (GHG) emissions in all phases, excluding the operation phase. However, investigations of the compatibility of GSHPs in tropical regions have been limited to evaluations based on energy consumption in the operation phase, leading to a lack of clarity regarding the contribution of increased initial cost and GHG emissions to the environmental compatibility and economic feasibility based on lifecycle aspects. Thus, this study aimed to evaluate the GHG emissions over the entire life cycle and the cost payback time of a 20-kW capacity GSHP in Bangkok, Thailand, designed with a predicted 50-year heat sink temperature. The results confirmed that the required scale of GHEs is twice as large in tropical regions as in mid‒high latitude regions; nevertheless, the energy-saving of the GSHP resulted in an 8.8 % reduction in GHG emissions over the entire life cycle compared to an air source heat pump. However, the capital investment cannot be recovered within the lifetime of the GSHP, requiring incentives and cost reduction due to the growth of the GSHP market.

Experimental and numerical study on temperature control performance of phase change material heat sink

With the increasing power consumption of electronic products, the rising temperature leads to the deterioration of working environment and the reduction of service life. In order to control the temperature rise of electronic products, in this paper, the heat sinks with phase change material (PCM) and honeycomb metal were designed. And their performance was compared with that of the original heat sink (without PCM and honeycomb metal) then studied under various working conditions. Paraffin (n-eicosane) and prepared low melting point alloy were filled into the heat sink with honeycomb metal. The temperature control performance of heat sink was tested experimentally under different heating power. A two-dimensional heat transfer mathematical model of honeycomb metal PCM heat sink was established and solved numerically. The numerical results were compared with experimental data to verify the mathematical model. The results demonstrate that PCM heat sinks effectively controls the temperature of electronic devices and the low melting point alloy makes heat sink better performance than paraffin. Honeycomb metal further decreases the temperature of the paraffin heat sink by up to 3.6 °C, and extends the effective working time of the alloy heat sink by 14 %. The performance of the low melting point honeycomb metal heat sink is superior to that of the paraffin honeycomb metal heat sink at high heating power, and is close to the latter at low heating power. The effective working time of PCM honeycomb metal heat sink is significantly extended when the PCM melting point is close to the limit temperature, especially at high heating power and for the PCM with low thermal conductivity. This study provides valuable reference for temperature control design of electronic products.

Significant thermal upgrade via cascade high temperature heat pump with low GWP working fluids

High temperature heat pump is a promising solution for efficient high temperature heat supply. However, the poor performance when it operates in large temperature lift hinders it from utilizing low temperature waste heat. To solve this problem, a cascade high temperature heat pump with economized vapor injection was established and a simulation model was developed accordingly. The tests were conducted using R134a/R245fa and R1234ze(E)/HP-1 at heat source temperature from 5 to 30 °C and heat sink temperature from 90 to 120 °C, with the coefficient of performance (COP) varying in the range of 1.72–2.73 and 1.77–2.75, respectively. The COP about 2.20 was achieved with R1234ze(E)/HP-1 at optimal intermediate temperature and optimal economized vapor injection pressure when the temperature lift is 100 °C. In the simulated case study, the heat pump water boiler based on the experimental prototype decreases CO2 emission by 62.8 % compared to electric boiler. Moreover, using low GWP working fluids reduces 1.32 × 104 kg direct CO2 emission in TEWI. Under the current technological, pricing, and operational condition, it takes 16 years for heat pump to have economic benefit over electric boiler, but this duration can be shortened with reduced initial cost, improved COP, and increased operating hours and electricity price. In summary, this work presented a high-efficient, environmentally friendly, and economically viable cascade high temperature heat pump system which has potential to utilize the abundant environmental heat source and deliver high temperature heat, being an alternative to the conventional heat generation equipment such as boilers.

Nanofluids in microchannel heat sinks for efficient flow cooling of power electronic devices

Nanofluids hold significant potential in the field of heat transfer intensification. The objective of this paper is to investigate the thermal-hydraulic characteristics of Ag, SiO2, and Al2O3 nanofluids in rectangular (MC-R), trapezoidal (MC-T), and omega-shaped (MC-O) microchannel heat sinks (MCHSs) through conjugate numerical simulations under a constant heat flux of 100 W/cm2. Water was used as the base fluid, and nanoparticle volume fraction ranged from 0 to 6 %. The average heat transfer coefficient (HTC), Nusselt number, thermal resistance, pressure drop, and pump power as a function of Reynolds number are studied for different nanofluids and cross-sectional shapes in microchannels. The overall performance is also characterized by thermal performance factor, coefficient of performance (COP), and entropy generation analysis. The simulation results show that adding Al2O3 nanoparticles with a volume fraction of 6 % in MC-R at a Reynolds number of 500 results in a substantial 12.3 % increase in the average HTC and an approximately 8 % reduction in total thermal resistance compared to pure water. For the same nanofluid, MC-O exhibits the highest convective HTC, the highest Nusselt number, and the lowest maximum heat sink temperature. The total entropy generation in the MCHSs decreases obviously with increasing Reynolds number. MC-O has the smallest total entropy generation, meaning it has the optimal flow and heat transfer irreversibility. These findings can not only provide valuable guidance for the rational design of MCHSs but also hold significant implications for the effective cooling of microelectronic components via nanofluid-based thermal management technology.

Electrochemical heat engine based on neutralization flow battery for continuous low-grade heat harvesting

An enormous amount of energy is wasted annually in the form of low-grade heat with a temperature below 100 °C. Recently, studies on heat harvesting have focused on semiconductor-based devices, but nowadays, electrochemical devices based on a thermally regenerative cycle (TREC) are growing in importance due to their superior thermoelectric power. Among them, TRECs based on flow batteries (TREC-FB) are especially attractive since they offer more flexibility for heat harvesting and an opportunity for continuous heat-to-power (HTP) conversion. However, this technology struggles due to the high cost of the flow batteries they are based on, particularly the costly electrolyte solutions. We offer a novel approach for continuous heat harvesting based on the emerging technology of the neutralization flow battery (NFB) with low-cost and highly soluble electrolytes, which consists of two hydrogen electrodes immersed in acid and base solutions. Since values of both electrodes’ temperature coefficient differ, NFB can be used for heat harvesting: the cell temperature coefficient varies in the range of 0.64–1.1 mV K−1. Here, we present both intermittent and continuous TREC based on NFB, with a focus on the latter due to its convenience. Our study on continuous heat harvesting shows that for a temperature difference between the heat source and heat sink of 25 °C, one can achieve power of 10–24 μW cm−2, and efficiency of 1.4–2.9 % even without any recuperation. Alternatively, increasing the temperature difference to 55 °C results in a 6-fold increase in power at 1.6–3.5 % efficiency. We found that due to the low freezing point of the electrolytes, one can obtain even higher HTP performance if the heat sink temperature is about 0 °C. Additionally, we examined NFB performance under various temperatures and proposed low-grade heat harnessing using intermittent NFB heating/cooling to enhance its cycling performance. We believe that the proposed approaches facilitate further development of high-performance TREC-FB and thereby extend the possibilities for heat harvesting.

PERFORMANCE EVALUATION OF HOT AIR THERMOELECTRIC GENERATOR USING BIOMASS ENERGY SOURCE

Thermoelectric generators are solid-state devices that convert heat into electricity using the Seebeck effect, when there is a temperature difference across a thermoelectric material. This research designed an experimentally tested a thermoelectric hot air generator using sixteen SP1848-27145 modules in two parallel strings. The system consists of a biomass combustion chamber, hot air exhauster, hot and cold side heat exchangers. Voltage, current and temperatures in the combustion chamber, hot air heat exhauster, hot side heat exchanger and cold side heat sink were measured. The hot air exhauster, hot side heat sink and cold side maximum temperatures are 178.3°C, 69.2°C and 44.5°C respectively yielding an open circuit voltage of 64 V and current of 1.99 A in the course of the experiment. The thermal performance of the designed hot air exhauster, hot side heat exchanger and cold side heat were simulated using ANSYS Fluent, for pictorial representation of their temperature contours.

Single-mode interband cascade laser based on V-coupled cavity with 210 nm wavelength tuning range near 3 µm.

Interband cascade lasers (ICLs) are efficient and compact mid-infrared (3-5 µm) light sources with many applications. By enhancing the coupling coefficient and using a type-I ICL wafer, single-mode ICLs were demonstrated based on V-coupled cavity with significantly extended tuning range and with a side mode suppression ratio (SMSR) exceeding 35 dB in continuous wave operation near 3 µm. A V-coupled cavity ICL exhibited a wavelength tuning up to 67 nm at a fixed temperature, and the total tuning range exceeds 210 nm when the heat sink temperature is adjusted from 80 to 180 K. The realization of single-mode in such a wide temperature range with a tuning range exceeding 210 nm verified the advantage of V-coupled cavity ICLs for effective detection of multiple gas species. This is very different from the conventional distributed feedback (DFB) laser where the single-mode operation is restricted to a narrow temperature range, in which the match between the gain peak and the DFB grating period determined wavelength is required. Another V-coupled cavity ICL is tuned over 120 nm from 2997.56 nm to 3117.50 nm with the heat-sink temperature varied from 210 K to 240 K, over 100 K higher than the previously reported maximum operating temperature for V-coupled cavity ICLs.